Magnetic resonance imaging (MRI)-guided robotic systems offer great potential for new minimally invasive medical tools, including MRI-powered miniature robots. By re-purposing the imaging hardware of an MRI scanner, the magnetic miniature robot could be navigated into the remote part of the patient's body without needing tethered endoscopic tools. However, state-of-art MRI-powered magnetic miniature robots have limited functionality besides navigation. Here, we propose an MRI-powered magnetic miniature capsule robot benefiting from acoustic streaming forces generated by MRI-guided high-intensity focus ultrasound (HIFU) for controlled drug release. Our design comprises a polymer capsule shell with a submillimeter-diameter drug-release hole that captures an air bubble functioning as a stopper. We use the HIFU pulse to initiate drug release by removing the air bubble once the capsule robot reaches the target location. By controlling acoustic pressure, we also regulate the drug release rate for multiple locations targeting during navigation. We demonstrated that the proposed magnetic capsule robot could travel at high speed, up to 1.13 cm/s in ex vivo porcine small intestine, and release drug to multiple target sites in a single operation, using a combination of MRI-powered actuation and HIFU-controlled release. The proposed MRI-guided microrobotic drug release system will greatly impact minimally invasive medical procedures by allowing on-demand targeted drug delivery.

The introduction of neuroendoscopy, microneu- rosurgery, neuronavigation, and intraoperative imaging for surgical operations has made significant improvements over other traditionally invasive surgical techniques. The integration of magnetic resonance imaging (MRI)-driven surgical devices with intraoperative imaging and endoscopy can enable further advancements in surgical treatments and outcomes. This work proposes the design and development of an MRI-driven endo- scope leveraging the high (3–7 T), external magnetic field of an MR scanner for heat-mitigated steering within the ventricular system of the brain. It also demonstrates the effectiveness of a Lorentz force-based grasper for diseased tissue manipulation and ablation. Feasibility studies show the neuroendoscope can be steered precisely within the lateral ventricle to locate a tumor using both MRI and endoscopic guidance. Results also indicate grasping forces as high as 31 mN are possible and power inputs as low as 0.69 mW can cause cancerous tissue ablation. These findings enable further developments of steerable devices using MR imaging integrated with endoscopic guidance for improved outcomes.

Electromagnetic field gradients generated by magnetic resonance imaging (MRI) devices pave the way to power untethered magnetic robots remotely. This innovative use of MRI devices allows exerting magnetic pulling forces on untethered magnetic robots, which could be used for navigation, diagnosis, drug delivery and therapeutic procedures inside a human body. So far, MRI-powered untethered magnetic robots lack simultaneous position and orientation control inside three-dimensional (3D) fluids, and therefore, their control has been limited to 3-DoF position control. In this paper, we present a path-planning-based 5-DoF control algorithm to steer and control an MRI-powered untethered robot's position and orientation simultaneously in 3D workspaces in fluids. Eventhough the simulation results show that the proposed optimal controller can successfully control the robot for 5-DoF, in the experiments, we observe a reduced 5-DoF controllability due to the robot manufacturing errors, which result in pitch angle to remain at around the neutral pitching angle at the steady state. The proposed controller was evaluated to track four different paths (linear, planar-horizontal, planar-vertical and 3D paths) generated by 3D Bezier curves. The worst-case path-tracking error was observed for 3D path-following experiments. For this case, the position-tracking error was 2.7±1.8 mm, and the orientation-tracking error was 13.5± 28.7 and 3.7± 10.2 degrees for yaw and pitch angles, respectively. The overall path is completed within 19.6 seconds with 23.6 mm overall displacement and 61.2 and 41.2 degrees of yaw and pitch angle rotation, respectively. Such robots can be used in future MRI-powered active imaging, laser surgery and biopsy robots inside a fluid-filled stomach type of organs.

Magnetic resonance imaging (MRI) devices provide magnetic field gradients, which can be used to remotely actuate magnetic robots that may one day carry out medical tasks, such as diagnosis, drug delivery, or therapeutic-laser-based procedures, in addition to the high-resolution tissue images for diagnosis. However, in comparison with magnetic systems that are custom designed solely for magnetic actuation, the magnetic environment of an MRI device is constrained by the requirements for imaging, which reduces the number of active degrees of freedom available for magnetic actuation. Moreover, the current MRI-powered untethered robots are limited to translational magnetic pulling in three dimensions only. In this article, we propose a design for an untethered magnetic robot that can rotate in a three-dimensional liquid volume in magnetic environments, like those in MRI devices. We demonstrate rotational actuation of our robot inside a commercially available MRI gradient coil. Two kinds of near-neutrally buoyant robot designs are proposed, where each design has particular advantages. Design methodologies, analysis of rotational performance, closed-loop orientation control of up to 2.51 rad of orientation change with maximum net displacement of 18.4 mm, and angular velocity control (0.2-0.63 rad/s) of these robot designs are presented.

This paper proposes a method of simultaneously calibrating magnetic localization and actuation systems for magnetically actuated robots. In this method, uncalibrated magnetic localization and actuation systems are calibrated simultaneously with minimal human intervention, which enables self-calibration, flexible reconfiguration, and long-term correctness of the system parameters. This method employs a bundle adjustment framework using a quadratic measurement model for sensors and the magnetic dipole model for actuators. The proposed method has been verified in comparison with finite element simulations and existing calibration methods for magnetic actuators and sensor arrays. In the experiments, the determinant of coefficient (R2value) was 99.84% for the sensor system and 99.45% for the actuator system after the calibration, comparable with individual state-of-art calibration methods of calibrating magnetic actuators and sensor arrays. This method has potential to improve the reconfigurability and long-term accuracy of magnetic robot localization and actuation systems, such as magnetically actuated capsule endoscopes.

Animals can incorporate large numbers of actuators because of the characteristics of muscles; whereas, robots cannot, as typical motors tend to be large, heavy, and inefficient. However, shape-memory alloys (SMA), materials that contract during heating because of change in their crystal structure, provide another option. SMA, though, is unidirectional and therefore requires an additional force to reset (extend) the actuator, which is typically provided by springs or antagonistic actuation. These strategies, however, tend to limit the actuator's work output and functionality as their force-displacement relationships typically produce increasing resistive force with limited variability. In contrast, magnetic springs-composed of permanent magnets, where the interaction force between magnets mimics a spring force-have much more variable force-displacement relationships and scale well with SMA. However, as of yet, no method for designing magnetic springs for SMA-actuators has been demonstrated. Therefore, in this paper, we present a new methodology to tailor magnetic springs to the characteristics of these actuators, with experimental results both for the device and robot-integrated SMA-actuators. We found magnetic building blocks, based on sets of permanent magnets, which are well-suited to SMAs and have the potential to incorporate features such as holding force, state transitioning, friction minimization, auto-alignment, and self-mounting. We show magnetic springs that vary by more than 3 N in 750 $\mu$m and two SMA-actuated devices that allow the MultiMo-Bat to reach heights of up to 4.5 m without, and 3.6 m with, integrated gliding airfoils. Our results demonstrate the potential of this methodology to add previously impossible functionality to smart material actuators. We anticipate this methodology will inspire broader consideration of the use of magnetic springs in miniature robots and further study of the potential of tailored magnetic springs throughout mechanical systems.

A reliable, real time, multi-sensor fusion functionality is crucial for localization of actively controlled capsule endoscopy robots, which are an emerging, minimally invasive diagnostic and therapeutic technology for the gastrointestinal (GI) tract. In this study, we propose a novel multi-sensor fusion approach based on a particle filter that incorporates an online estimation of sensor reliability and a non-linear kinematic model learned by a recurrent neural network. Our method sequentially estimates the true robot pose from noisy pose observations delivered by multiple sensors. We experimentally test the method using 5 degree-of-freedom (5-DoF) absolute pose measurement by a magnetic localization system and a 6-DoF relative pose measurement by visual odometry. In addition, the proposed method is capable of detecting and handling sensor failures by ignoring corrupted data, providing the robustness expected of a medical device. Detailed analyses and evaluations are presented using ex vivo experiments on a porcine stomach model, proving that our system achieves high translational and rotational accuracies for different types of endoscopic capsule robot trajectories.

In the last decade, researchers and medical device companies have made major advances towards transforming passive capsule endoscopes into active medical robots. One of the major challenges is to endow capsule robots with accurate perception of the environment inside the human body, which will provide necessary information and enable improved medical procedures. We extend the success of deep learning approaches from various research fields to the problem of sensor fusion for endoscopic capsule robots in the case of asynchronous and asymmetric sensor data without any need of calibration between sensors. The results performed on real pig stomach datasets show that our method achieves high precision for both translational and rotational movements and contains various advantages over traditional sensor fusion techniques.

Many robots make use of gravitational potential energy, generated by another mode, to enhance mobility through gliding locomotion. However, unstructured environments can create situations in which the initial conditions for steady-state gliding cannot be achieved; for example, jumping out of a hole, where the obstacle is very close to the robot. This paper suggests an optimization methodology for finding airfoil configurations and control strategies to maximize the effective non-steady-state gliding ratio for the most challenging initial condition, that of zero velocity. Parameters for the optimization are a location of a robot's center-of-mass in relation to its center-of-pressure and, through the addition of a tail, an active pitch control strategy. The optimal center-of-mass location produces the best passive gliding performance (morphological intelligence), and the optimal control strategy improves the gliding distance. Due to the aerodynamic complexities of modeling the collapsible airfoils, we find the optimal location of the center-of-mass from gliding experiments performed on the robot at different center-of-mass locations and initial pitch angles. An optimal location of the center-of-mass was found to be 40% of the wing chord for our robotic platform; measured from the wing's leading edge. The optimal location has a wide range of initial pitch angles which result in stable, yet non-steady-state, gliding behaviors. The morphological intelligence built into our robotic platform creates two observable dynamic behaviors, that of horizontal velocity gain and sink rate minimization. We then estimate the drag coefficients from the experiments, and conduct dynamic simulations to optimize the pitch control strategy. The design methodology presented here can enhance the non-steady-state gliding performance of a broad range of gliding robots, and the control strategy can further enhance performance on those which utilize an active tail.

Reliable and real-time 3D reconstruction and localization functionality is a crucial prerequisite for the navigation of actively controlled capsule endoscopic robots as an emerging, minimally invasive diagnostic and therapeutic technology for use in the gastrointestinal (GI) tract. In this study, we propose a fully dense, non-rigidly deformable, strictly real-time, intraoperative map fusion approach for actively controlled endoscopic capsule robot applications which combines magnetic and vision-based localization, with non-rigid deformations based frame-to-model map fusion. The performance of the proposed method is evaluated using four different ex-vivo porcine stomach models. Across different trajectories of varying speed and complexity, and four different endoscopic cameras, the root mean square surface reconstruction errors vary from 1.58 to 2.17 cm.

In the last decade, many medical companies and research groups have tried to convert passive capsule endoscopes as an emerging and minimally invasive diagnostic technology into actively steerable endoscopic capsule robots which will provide more intuitive disease detection, targeted drug delivery and biopsy-like operations in the gastrointestinal(GI) tract. In this study, we introduce a fully unsupervised, realtime odometry and depth learner for monocular endoscopic capsule robots. We establish the supervision by warping view sequences and assigning the re-projection minimization to the loss function, which we adopt in multi-view pose estimation and single-view depth estimation network. Detailed quantitative and qualitative analyses of the proposed framework performed on non-rigidly deformable ex-vivo porcine stomach datasets proves the effectiveness of the method in terms of motion estimation and depth recovery.

We use multiple spinning micro-rafts at the air-water interface as mobile microrobot collectives and present here their collective behaviors, including navigating around anchored obstacles, and trapping and transporting floating objects. The 3D-printed micro-rafts are circular disKS of 100 μm in diameter and have parametrically defined undulating edge profile. The study of their local interactions, manifested by the pairwise interactions between micro-rafts, reveals competing magnetic and capillary interactions that keep the collectives in their dynamic state. Using collectives of 7, 19, and 36 micro-rafts and micro-channels between millimeter-sized posts, we demonstrate the effects of the size of the collectives, the size of the obstacles, and maneuver strategies on the collective navigation. Employing methods from information theory, we show that the pairwise mutual information of the collectives increases significantly during the channel-crossing as a result of the additional constraints of the channel walls on the collectives. Finally, we demonstrate the trapping of 1-mm-diameter polystyrene bead and the trapping and transporting of 600~μm-wide pm.

Ingestible wireless capsule endoscopy is an emerging minimally invasive diagnostic technology for inspection of the GI tract and diagnosis of a wide range of diseases and pathologies. Medical device companies and many research groups have recently made substantial progresses in converting passive capsule endoscopes to active capsule robots, enabling more accurate, precise, and intuitive detection of the location and size of the diseased areas. Since a reliable real time pose estimation functionality is crucial for actively controlled endoscopic capsule robots, in this study, we propose a monocular visual odometry (VO) method for endoscopic capsule robot operations. Our method lies on the application of the deep recurrent convolutional neural networks (RCNNs) for the visual odometry task, where convolutional neural networks (CNNs) and recurrent neural networks (RNNs) are used for the feature extraction and inference of dynamics across the frames, respectively. Detailed analyses and evaluations made on a real pig stomach dataset proves that our system achieves high translational and rotational accuracies for different types of endoscopic capsule robot trajectories.

Despite significant progress achieved in the last decade to convert passive capsule endoscopes to actively controllable robots, robotic capsule endoscopy still has some challenges. In particular, a fully dense three-dimensional (3D) map reconstruction of the explored organ remains an unsolved problem. Such a dense map would help doctors detect the locations and sizes of the diseased areas more reliably, resulting in more accurate diagnoses. In this study, we propose a comprehensive medical 3D reconstruction method for endoscopic capsule robots, which is built in a modular fashion including preprocessing, keyframe selection, sparse-then-dense alignment-based pose estimation, bundle fusion, and shading-based 3D reconstruction. A detailed quantitative analysis is performed using a non-rigid esophagus gastroduodenoscopy simulator, four different endoscopic cameras, a magnetically activated soft capsule robot, a sub-millimeter precise optical motion tracker, and a fine-scale 3D optical scanner, whereas qualitative ex-vivo experiments are performed on a porcine pig stomach. To the best of our knowledge, this study is the first complete endoscopic 3D map reconstruction approach containing all of the necessary functionalities for a therapeutically relevant 3D map reconstruction.

Most demonstrated mobile microrobot tasks so far have been achieved via pick-and-placing and dynamic trapping with teleoperation or simple path following algorithms. In our previous work, an untethered magnetic microgripper has been developed which has advanced functions, such as gripping objects. Both teleoperated manipulation in 2D and 3D have been demonstrated. However, it is challenging to control the magnetic microgripper to carry out manipulation tasks, because the grasping of objects so far in the literature relies heavily on teleoperation, which takes several minutes with even a skilled human expert. Here, we propose a new spin-walking locomotion and an automated 2D grasping motion planner for the microgripper, which enables time-efficient automatic grasping of microobjects that has not been achieved yet for untethered microrobots. In its locomotion, the microgripper repeatedly rotates about two principal axes to regulate its pose and move precisely on a surface. The motion planner could plan different motion primitives for grasping and compensate the uncertainties in the motion by learning the uncertainties and planning accordingly. We experimentally demonstrated that, using the proposed method, the microgripper could align to the target pose with error less than 0.1 body length and grip the objects within 40 seconds. Our method could significantly improve the time efficiency of micro-scale manipulation and have potential applications in microassembly and biomedical engineering.

Magnetic untethered millirobots, which are actuated and controlled by remote magnetic fields, have been proposed for medical applications due to their ability to safely pass through tissues at long ranges. For example, magnetic resonance imaging (MRI) systems with a 3-7 T constant unidirectional magnetic field and 3D gradient coils have been used to actuate magnetic robots. Such magnetically constrained systems place limits on the degrees of freedom that can be actuated for untethered devices. This paper presents a design and actuation methodology for a magnetic millirobot that exhibits both position and orientation control in 2D under a magnetic field, dominated by a constant unidirectional magnetic field as found in MRI systems. Placing a spherical permanent magnet, which is free to rotate inside the millirobot and located away from the center of mass, allows the generation of net forces and torques with applied 3D magnetic field gradients. We model this system in a 3D planar case and experimentally demonstrate open-loop control of both position and orientation by the applied 2D field gradients. The actuation performance is characterized across the most important design variables, and we experimentally demonstrate that the proposed approach is feasible.

Robotic systems that are soft or incorporate soft actuators are well suited for operation in unstructured environments and for safe interactions with fragile objects. The majority, however, are tethered or burdened with bulky payloads of pumps and compressors. In a recent article we presented a sealed, inflated actuator composed of fluidically connected membrane dielectric elastomer actuators capable of large, repeatable, and stable deformations. Each membrane could switch between two identical volumes, and maintain its shape when an applied voltage was removed. Here we extend our previous work by simulating and demonstrating asymmetric stable deformations. In an experimental two-membrane setup, the membranes experience large and significantly different area strains of >100% and >550% when transitioning between stable states. With the addition of more membranes, this asymmetry can increase the number of discrete stable membrane sizes, allowing more complex control when later implemented in a mechanism.

Magnetotactic bacteria have the potential to controllably reach stagnant fluids inside the human body and achieve targeted drug delivery. In this application, motion of the magnetotactic bacteria is influenced by the near-surface effects such as the background flows and surface interactions. Here, we provide a hydrodynamic model of bipolarly-flagellated magnetotactic bacteria (Magnetospirillum gryphiswaldense strain MSR-1) based on the resistive-force theory to resemble the helical body and the two flagella bundles, and investigate their swimming characteristics in two environments, i.e., free-space and near flat walls. The free-space is studied using capillary tubes with depth of 200 μm, whereas the effect of the flat walls is investigated using microfluidic chips with depth of 5 μm. We find that the linear speeds of bacteria near- and far-surface are 36±16.4 μm/s (mean±s.d.) and 46±6.8 μm/s, respectively, whereas their respective angular velocities are 12.5±5.7 rad/s and 13.5±5.0 rad/s.

This paper presents a magnetically actuated soft capsule endoscope for fine-needle aspiration biopsy (B-MASCE) in the upper gastrointestinal tract. A thin and hollow needle is attached to the capsule, which can penetrate deeply into tissues to obtain subsurface biopsy sample. The design utilizes a soft elastomer body as a compliant mechanism to guide the needle. An internal permanent magnet provides a means for both actuation and tracking. The capsule is designed to roll towards its target and then deploy the biopsy needle in a precise location selected as the target area. B-MASCE is controlled by multiple custom-designed electromagnets while its position and orientation are tracked by a magnetic sensor array. In in vitro trials, B-MASCE demonstrated rolling locomotion and biopsy of a swine tissue model positioned inside an anatomical human stomach model. It was confirmed after the experiment that a tissue sample was retained inside the needle.

Fluidic actuators allow versatile, agile, and powerful motions and are commonly applied in robotics and automation. Likewise, many biological systems use fluidic actuators implemented with tissue for a wealth of tasks and performances. Spiders for example apply a hybrid mechanism of hydraulically actuated joint extension and muscle-based joint flexion to produce movement in two of their seven leg joints. Here, we present a novel spider-inspired joint mechanism employing both pneumatics and electrically-actuated tendons capable of strong, dynamic, and rapid joint movement. The implementation of the joint is closely inspired by those seen in real spiders, with a foldable structured membrane that effectively transfers all the energy from pressure to torque as the leg unfolds. To evaluate the mechanism we derived static joint models and a simple jumping model, and conducted equivalent experimental tests with a prototype of a single jumping leg robot. Besides applications in robot locomotion, the implementation and modeling of the spider-inspired joint mechanism can be utilized to further explore dynamics and functional biomechanics in spiders. In the future, we hope to use this platform to answer questions related to the impressive jumping and locomotion performances of real arachnids, and explore what morphological traits lie behind efficient spider locomotion at different size scales.

In travelling towards the oviducts, sperm cells undergo transitions between planar to helical flagellar propulsion by a beating tail based on the viscosity of the environment. In this work, we aim to model and mimic this behaviour in low Reynolds number fluids using externally actuated soft robotic sperms. We numerically investigate the effects of transition between planar to helical flagellar propulsion on the swimming characteristics of the robotic sperm using a model based on resistive-force theory to study the role of viscous forces on its flexible tail. Experimental results are obtained using robots that contain magnetic particles within the polymer matrix of its head and an ultra-thin flexible tail. The planar and helical flagellar propulsion are achieved using in-plane and out-of-plane uniform fields with sinusoidally varying components, respectively. We experimentally show that the swimming speed of the robotic sperm increases by a factor of 1.4 (fluid viscosity 5 Pa.s) when it undergoes a controlled transition between planar to helical flagellar propulsion, at relatively low actuation frequencies.

We use electrospinning to fabricate sperm-shaped magnetic microrobots with a range of diameters from 50 μm to 500 μm. The variables of the electrospinning operation (voltage, concentration of the solution, dynamic viscosity, and distance between the syringe needle and collector) to achieve beading effect are determined. This beading effect allows us to fabricate microrobots with similar morphology to that of sperm cells. The bead and the ultra-fine fiber resemble the morphology of the head and tail of the sperm cell, respectively. We incorporate iron oxide nanoparticles to the head of the sperm-shaped microrobot to provide a magnetic dipole moment. This dipole enables directional control under the influence of external magnetic fields. We also apply weak (less than 2 mT) oscillating magnetic fields to exert a magnetic torque on the magnetic head, and generate planar flagellar waves and flagellated swim. The average speed of the sperm-shaped microrobot is calculated to be 0.5 body lengths per second and 1 body lengths per second at frequencies of 5 Hz and 10 Hz, respectively. We also develop a model of the microrobot using elastohydrodynamics approach and Timoshenko-Rayleigh beam theory, and find good agreement with the experimental results.

Many highly dynamic novel mobile robots have been developed being inspired by animals. In this study, we are inspired by a basilisk lizard's ability to run and steer on water surface for a hexapedal robot. The robot has an active tail with a circular plate, which the robot rotates to steer on water. We dynamically modeled the platform and conducted simulations and experiments on steering locomotion with a bang-bang controller. The robot can steer on water by rotating the tail, and the controlled steering locomotion is stable. The dynamic modelling approximates the robot's steering locomotion and the trends of the simulations and experiments are similar, although there are errors between the desired and actual angles. The robot's maneuverability on water can be improved through further research.

Vibration-driven locomotion has been widely used for crawling robot studies. Such robots usually have a vibration motor as the actuator and a fibrillar structure for providing directional friction on the substrate. However, there has not been any studies about the effect of fiber structure on robot crawling performance. In this paper, we develop Fiberbot, a custom made mini vibration robot, for studying the effect of fiber angle on robot velocity, steering, and climbing performance. It is known that the friction force with and against fibers depends on the fiber angle. Thus, we first present a new fabrication method for making millimeter scale fibers at a wide range of angles. We then show that using 30° angle fibers that have the highest friction anisotropy (ratio of backward to forward friction force) among the other fibers we fabricated in this study, Fiberbot speed on glass increases to 13.8±0.4 cm/s (compared to ν = 0.6±0.1 cm/s using vertical fibers). We also demonstrate that the locomotion direction of Fiberbot depends on the tilting direction of fibers and we can steer the robot by rotating the fiber pad. Fiberbot could also climb on glass at inclinations of up to 10° when equipped with fibers of high friction anisotropy. We show that adding a rigid tail to the robot it can climb on glass at 25° inclines. Moreover, the robot is able to crawl on rough surfaces such as wood (ν = 10.0±0.2 cm/s using 30° fiber pad). Fiberbot, a low-cost vibration robot equipped with a custom-designed fiber pad with steering and climbing capabilities could be used for studies on collective behavior on a wide range of topographies as well as search and exploratory missions.

In this work, we examine two design modifications to a tethered motor-driven flapping-wing system. Previously, we had demonstrated a simple mechanism utilizing a linear transmission for resonant operation and direct drive of the wing flapping angle for control. The initial two-wing system had a weight of 2.7 grams and a maximum lift-to-weight ratio of 1.4. While capable of vertical takeoff, in open-loop flight it demonstrated instability and pitch oscillations at the wing flapping frequency, leading to flight times of only a few wing strokes. Here the effect of vertical wing offset as well as an alternative multi-wing layout is investigated and experimentally tested with newly constructed prototypes. With only a change in vertical wing offset, stable open-loop flight of the two-wing flapping system is shown to be theoretically possible, but difficult to achieve with our current design and operating parameters. Both of the new two and four-wing systems, however, prove capable of flying to the end of the tether, with the four-wing system prototype eliminating disruptive wing beat oscillations.

In this work, we examine several wing designs for a motor-driven, flapping-wing micro air vehicle capable of liftoff. The full system consists of two wings independently driven by geared pager motors that include a spring in parallel with the output shaft. The linear transmission allows for resonant operation, while control is achieved by direct drive of the wing angle. Wings used in previous work were chosen to be fully rigid for simplicity of modeling and fabrication. However, biological wings are highly flexible and other micro air vehicles have successfully utilized flexible wing structures for specialized tasks. The goal of our study is to determine if wing flexibility can be generally used to increase wing performance. Two approaches to lift improvement using flexible wings are explored, resonance of the wing cantilever structure and dynamic wing twisting. We design and test several wings that are compared using different figures of merit. A twisted design improved lift per power by 73.6% and maximum lift production by 53.2% compared to the original rigid design. Wing twist is then modeled in order to propose optimal wing twist profiles that can maximize either wing efficiency or lift production.

Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size goes down to the order of a single cell, previously inaccessible body sites would become available for high-resolution in situ and in vivo manipulations. This unprecedented direct access would enable an extensive range of minimally invasive medical operations. Here, we provide a comprehensive review of the current advances in biomedical untethered mobile milli/microrobots. We put a special emphasis on the potential impacts of biomedical microrobots in the near future. Finally, we discuss the existing challenges and emerging concepts associated with designing such a miniaturized robot for operation inside a biological environment for biomedical applications.

One major challenge for untethered micro-scale mobile robotics is the manipulation of external objects in the robot's three-dimensional (3D) work environment. Here, we present a method to use the capillary force at a solid-liquid-gas interface to reversibly attach objects to a mobile magnetic microrobot. This is accomplished by the addition of a cavity in the hydrophobic microrobot, in which an air bubble is captured when the microrobot is placed in a water environment. The extension of the air bubble from the cavity is adjusted dynamically by controlling the pressure of the workspace environment. A peak switching ratio between the maximum and minimum gripping forces of 14:1 is shown for controlled attachment/detachment experiments, which allows for reliable pick-and-place operation. This work introduces an analytical capillary adhesion model and demonstrates control of the bubble size for pick-and-place gripping. A proof-of-concept demonstration of 3D manipulation in a fluidic environment shows the potential of capillary gripping for future use in confined environments such as inside microfluidic devices for transportation or assembly of hydrophobic objects.

This paper presents a novel synthesis method for the design of micro-scale robotic flexure mechanisms. A structural optimization method, termed the mechanism-based approach, is used to identify the optimal topology and shape of the flexure mechanisms based on their lump stiffness characteristics. Using several different fitness functions, several optimal flexure designs have been synthesized for use in millimeter-scale mobile grippers (μ-grippers). The stiffness characteristics of the optimal μ-grippers are shown to be better than the thin-beam designs developed using human intuition. Two large-scale prototypes are constructed and experiments are conducted to validate the stiffness analysis. The experimental results are within 20% of the analytical expectations. As a proof of concept, at-scale μ-grippers are constructed based on photolithography and replica molding methods, and demonstrated in simple actuation. The optimal μ-grippers can be applicable for cell manipulations in future works.

This paper proposes GeckoGripper, a novel soft, inflatable gripper based on the controllable adhesion mechanism of gecko-inspired micro-fiber adhesives, to pick-and-place complex and fragile non-planar or planar parts serially or in parallel. Unlike previous fibrillar structures that use peel angle to control the manipulation of parts, we developed an elastomer micro-fiber adhesive that is fabricated on a soft, flexible membrane, increasing the adaptability to non-planar three-dimensional (3D) geometries and controllability in adhesion. The adhesive switching ratio (the ratio between the maximum and minimum adhesive forces) of the developed gripper was measured to be around 204, which is superior to previous works based on peel angle-based release control methods. Adhesion control mechanism based on the stretch of the membrane and superior adaptability to non-planar 3D geometries enable the micro-fibers to pick-and-place various 3D parts as shown in demonstrations.

This study presents the design of a novel minimalist liftoff-capable flapping-wing microaerial vehicle. Two wings are each directly driven by a geared pager motor by utilizing an elastic element for energy recovery, resulting in a maximum lift-to-weight ratio of 1.4 at 10 Hz for the 2.7 g system. Separate directly driven wings allow the system to both resonate and control individual wing flapping angle, reducing necessary power consumption, as well as allowing the production of roll and pitch body torques. With a series of varied prototypes, system performance is examined with change in wing offset from center of rotation and elastic element stiffness. Prototype liftoff is demonstrated with open loop driving a tethered prototype without guide wires. A dynamic model of the system is adapted and compared with the prototype experimental results for later use in prototype optimization.

Recent studies have been carried out for rotating single flexible flagellum: a possible propelling mechanism that has been adopted by several artificial microswimmers due to its relatively simple structure yet considerable propulsive force generation. In this paper, we introduce a miniature swimming robot design with multiple flexible artificial flagella that benefits from the increased number of flagella. The characteristic length of the robot body is less than 1 mm. Experimental characterization of swimming of the robot shows that swimming speed can be linearly improved solely by increasing the number of attached flagella, suggesting a new way for speed enhancement besides flagellum geometry optimization. In addition, a numerical model modified from the single, straight flexible flagellum case is further established to study propulsive force generation by nonstraight, flexible flagellum. A robot with multiple, sinusoidal flagella design is fabricated to demonstrate the capability of the proposed two-step photolithography-based microfabrication method to handle more complex flagella designs, which may enhance swimming performance.

In previous work, a proof-of-concept artificial flapper was devised by Campolo et al. to demonstrate that DC motors, in concert with compliant mechanisms, would be able to directly flap wings at relatively high frequencies and large angles without exceeding their operational limits. The prototype makes use of a pair of relatively long elastic strings as the compliant structures. In this article, we experimentally analyze the wing kinematics and efficiency of a more compact prototype, where small helical springs are implemented instead of elastic strings. Since the proof-of-concept prototype validated the quasi-sinusoidal assumption in spite of nonlinear aerodynamic damping, incorporating instantaneous wing kinematics into the analysis is not necessary, simplifying experiments and data processing. Along with wing kinematics and system efficiency, the possibility of controlling the wing pair to flap independently is evaluated as well.

Robots capable of hover flight in constrained indoor environments have many applications, however their range is constrained by the high energetic cost of airborne locomotion. Perching allows flying robots to scan their environment without the need to remain aloft. This paper presents the design of a mechanism that allows indoor flying robots to attach to vertical surfaces. To date, solutions that enable flying robot with perching capabilities either require high precision control of the dynamics of the robot, or a mechanism robust to high energy impacts. In this article, we propose a perching mechanism comprising a compliant deployable pad and a passive self-alignment system, that does not require any active control during the attachment procedure. More specifically, a perching mechanism using fibre-based dry adhesives was implemented on a 300 g flying platform. An adhesive pad was first modeled and optimized in shape for maximum attachment force at the low pre-load forces inherent to hovering platforms. It was then mounted on a deployable mechanism that stays within the structure of the robot during flight and can be deployed when a perching manoeuvre is initiated. Finally, the perching mechanism is integrated onto a real flying robot and successful perching manoeuvres are demonstrated as a proof of concept.

A major challenge for untethered micro-scale mobile robotics is the control of many agents in the same workspace for distributed operation. In this work, we present a new method to independently control multiple sub-mm microrobots in three dimensions (3D) using magnetic gradient based direct pulling as the 3D motion generation method. This is accomplished through the use of geometrically or magnetically distinct microrobots which assume different magnetization directions in a rotating magnetic field. Such diversity in design allows for different magnetic forces to be exerted on each, enabling path following with less than 370μm mean path deviation for a set of two microrobots of size 350μm and 1500μm. This addressability method could be used for the 3D control of a team of microrobots inside microfluidic channels or in the human body for localized therapy or diagnostics.

To address some of the challenges in modular micro-robotics, we present a new heat-activated bonding method for assembly. This bonding method quickly forms strong bonds through the use of thermoplastic or solder binding sites integrated into each module face, addressing problems of assembly strength and electrical conductivity. The strength of the bonds for each method are compared for different module styles, bonding conditions and breaking conditions in a destructive test. For 800μm modules, bond strengths of up to 500mN are observed with thermoplastic bonds, which indicates that the assemblies could be potentially used in high-force structural applications of programmable matter, microfluidic channels or healthcare. By magnetically functionalizing the modules using embedded magnetic particles, the modules are moved remotely for assembly using a magnetic coil system. In this way, a set of six modules are remotely assembled one-by-one into an arbitrary shape capable of locomotion to demonstrate the scalability and strength of the system.

This paper proposes a soft self-assembling modular matter, which is called SoftCubes where serially connected soft cubes can be extremely stretched by external tension and has a self-recovery capability to an originally designed 3-D shape. The developed soft modular matter has three main design features. First, entire modules of the 3-D assembled shape are serially connected. Such a structure allows all the modules to be disassembled and stretched by external tension. Second, the modules are made of soft stretchable elastomer. The soft-body of the modules provides a high flexibility and an extreme shape adaptation capability with the disassembled modules. Also, if the external tension is removed, the original 3-D shape is self-recovered by the elastic restoring force of soft-bodied modules. Finally, small permanent magnets are embedded in each module. The magnetic attraction between modules makes them self-assembled and precisely aligned with the neighbor modules in a lattice structure. The paper presents various analyses, simulations, and demonstrations about soft modular matter's shape reconfiguration to 1-D and self-recovery to 3-D. The designed soft modular matter could enable new applications as injectable medical implants and implantable modular devices.

In this paper, we present a 3-D localization method for a magnetically actuated soft capsule endoscope (MASCE). The proposed localization scheme consists of three steps. First, MASCE is oriented to be coaxially aligned with an external permanent magnet (EPM). Second, MASCE is axially contracted by the enhanced magnetic attraction of the approaching EPM. Third, MASCE recovers its initial shape by the retracting EPM as the magnetic attraction weakens. The combination of the estimated direction in the coaxial alignment step and the estimated distance in the shape deformation (recovery) step provides the position of MASCE in 3-D. It is experimentally shown that the proposed localization method could provide 2.0-3.7 mm of distance error in 3-D. This study also introduces two new applications of the proposed localization method. First, based on the trace of contact points between the MASCE and the surface of the stomach, the 3-D geometrical model of a synthetic stomach was reconstructed. Next, the relative tissue compliance at each local contact point in the stomach was characterized by measuring the local tissue deformation at each point due to the preloading force. Finally, the characterized relative tissue compliance parameter was mapped onto the geometrical model of the stomach toward future use in disease diagnosis.

We present a new scheme of remote addressable magnetic actuation for sub-mm microrobotics which uses the hysteresis characteristics of multiple magnetic materials to achieve advanced state control of many magnetic actuators sharing the same magnetic control inputs. Using this standard approach, remote magnetic actuation of a single magnet has been achieved for untethered motion control with a single magnetic control input. We propose the simultaneous use of multiple magnetic materials with varying hysteresis characteristics to effectively gain multiple control inputs as different applied magnetic field strengths. As a first experimental implementation of this idea, we present a set of three heterogeneous magnetic modules floating on a liquid surface which can be remotely reconfigured by application of a field of varying magnitude. As a second implementation, we present a team of up to six independently actuated walking microrobots made from a composite material whose net magnetic moment can be selectively turned on or off by application of a large magnetic field pulse. We also demonstrate a team of two addressable microrobots performing a task requiring cooperative teamwork. The presented concept providing multiple magnetic control inputs could be applicable in various areas of milli- or microrobotics to address multiple magnetic elements for motion or actuation control.

In this paper, we propose methods to control multiple untethered magnetic microrobots (called Mag-μBots), with all dimensions under 1 mm, without the need for a specialized surface. We investigate sets of Mag-μBots that are geometrically designed to respond uniquely to the same applied magnetic fields. By controlling the magnetic field waveforms, individual and subgroups of Mag-μBots are able to locomote in a parallel but dissimilar fashion. The control of geometrically dissimilar Mag-μBots and a group of identically fabricated Mag-μBots are investigated, and control strategies are developed for 1-D and 2-D motion. This is accomplished by learning the velocity response of each microrobot to various control signals and using the uniqueness of each microrobot response to achieve independent control. The effect of high-level control parameters are investigated in simulation and in experiments, and the simultaneous independent global positioning of two and three microrobots is demonstrated in 2-D space. As this control method is accomplished without the use of a specialized surface, it has potential applications in areas such as microfluidic systems and biomanipulation.

An active flexural hinge has been developed and incorporated into the transmission of a prototype flapping-wing robot. The multilayered flexure, which is constructed from a shape memory polymer and a polyimide film, showed controllable stiffness under change in temperature. At room temperature, the flexure had a bending stiffness of 572 mN·mm; when warmed to 70°C, the stiffness was 11 mN·mm. The resulting single-wing flapping system demonstrated up to an 80% change in generated lift without modification of the waveform of the main driving piezoelectric actuator. Such active stiffness tunable flexure joints could be applied to any flexural miniature mobile robot and device mechanisms.

This study develops autonomous manipulation strategies for a mobile untethered microrobot that operates on a 2-D surface in a fluidic environment. The microrobot, which is a permanent magnet, is under m in all dimensions and is actuated by oscillating external magnetic fields. Two types of manipulations are considered: 1) front pushing, where the microrobot pushes a micro-object by direct contact; and 2) side pushing, which can result in noncontact pushing, where the fluid flow fields that are generated by a translating microrobot are used to displace a micro-object. Physical models are provided to estimate the displacement of the micro-object due to the fluid motion. Model-based controllers to perform contact and noncontact manipulation are proposed, which iteratively correct emerging manipulation behaviors to improve performance. It is found that using a model-based solution as a feed-forward input, which is combined with a learning controller, can significantly improve micro-object pushing performance. Finally, we begin to address the problem to assemble two micro-objects together using the microrobot, which is only successful by using a side-pushing method.

This paper proposes a magnetically actuated soft capsule endoscope (MASCE) as a tetherless miniature mobile robot platform for diagnostic and therapeutic medical applications inside the stomach. Two embedded internal permanent magnets and a large external magnet are used to actuate the robot remotely. The proposed MASCE has three novel features. First, its outside body is made of soft elastomer-based compliant structures. Such compliant structures can deform passively during the robot-tissue contact interactions, which makes the device safer and less invasive. Next, it can be actively deformed in the axial direction by using external magnetic actuation, which provides an extra degree of freedom that enables various advanced functions such as axial position control, drug releasing, drug injection, or biopsy. Finally, it navigates in three dimensions by rolling on the stomach surface as a new surface locomotion method inside the stomach. Here, the external attractive magnetic force is used to anchor the robot on a desired location, and the external magnetic torque is used to roll it to another location, which provides a stable, continuous, and controllable motion. The paper presents design and fabrication methods for the compliant structures of the robot with its axial deformation and position control capability. Rolling-based surface locomotion of the robot using external magnetic torques is modeled, and its feasibility is tested and verified on a synthetic stomach surface by using a magnetically actuated capsule endoscope prototype.

In this paper, we present a shape-programmable magnetically actuated soft capsule robot for semi-implantable drug delivery applications. The shape of the proposed soft capsule is changed by an external magnetic field. To change the robot shape by an external permanent magnet, the relevant soft robot design features and required conditions are investigated using simulations and experiments. If the magnetic field is increased above a critical value, the capsule collapses to a sphere-like stable shape, which keeps the capsule inside the stomach all the time, and it cannot move to the duodenum by gastric peristalsis. We conducted experiments inside a synthetic stomach-like membrane to investigate how much tissue stress is induced by the soft capsule under emulated gastric peristalsis to show that the capsule induces no pain in the stomach and can sustain its spherical shape against external forces. Such a soft capsule can be used to release drugs, which can be contained on its body parts or inside a reservoir, while staying in the stomach. After depletion of the drug, a controlled rolling motion using the external magnetic field is proposed to recover the initial cylindrical shape. Then, the capsule can move into the duodenum by peristalsis and is discharged through the anus.

In this work, we develop methods for controlling multiple untethered magnetic micro-robots (called Mag-μBots), with all dimensions under 1 mm, without the need for a specialized surface. We investigate sets of Mag-μBots that are geometrically and magnetically designed to respond uniquely to the same magnetic fields. The responses of geometrically dissimilar Mag-μBots with similar magnetization and a group of identically-fabricated Mag-μBots are investigated. By controlling the magnetic field waveforms, individual and subgroups of Mag-μBots are able to locomote in a parallel but dissimilar fashion. Specifically, the pulsing frequency of the imposed driving magnetic fields is used as a selection method among the Mag-μBots. This method for accomplishing motion discrimination is discussed, modeled, and tested. Independent global positioning of two and three robots is demonstrated in two-dimensional space. While individual Mag-μBot velocities can be as high as 7 mm/s, the effective velocities during multi robot control are found to be up to 2 mm/s. As this control method is accomplished without the use of a specialized surface, it has potential applications in areas such as micro-fluidic systems and bio-manipulation.

Flapping-flight micro aerial vehicles (MAVs) pose an ongoing design problem to the scientific community, requiring careful consideration of both body structure and force production. Here, we examine a flapping MAV prototype with a passively rotating wing design. While at the current scale the lift force produced is not enough for liftoff, observing its performance under roll and pitch control can lead to insights on both the body design and the eventual free-flight implementation. As the production of roll and pitch torques are primarily uncoupled for this design, PID control is implemented in the roll and pitch directions individually on a custom designed single degree of freedom rig. By doing so, we show that the body structure is capable of sustaining independent wing amplitudes and that actuator input voltage bias shifting is successful experimentally on a dynamically driven wing. Through force compensation, the experimentally tested controller is mapped to a 1/2 scale simulated system, theoretically capable of free-flight. Though initial simulation results suggest high sensitivity to feedback noise, simulations show that decoupled roll and pitch controllers have potential as a minimal computational means for hovering and translational motion.

A primary challenge in the field of reconfigurable robotics is scaling down the size of individual robotic modules. We present a novel set of permanent magnet modules that are under 1 mm in all dimensions, called Mag-μMods, for use in a reconfigurable micro-system. The modules are actuated by oscillating external magnetic fields of several mT in strength, and are capable of locomoting on a 2-D surface. Multiple modules are controlled using an electrostatic anchoring surface, which selectively prevents specific modules from being driven by the external field, while allowing others to move freely. We model the processes of both assembling and disassembling two modules by analyzing the forces the modules experience, and experimentally verify the accuracy of the models. For disassembly, we employ electrostatic anchoring and externally applied magnetic torques to successfully separate the modules.

This paper presents a modular climbing robot connected by two passive compliant joints and featuring an active tail. The objective of this robot is to enable various internal and external transitions which are very challenging tasks for previously developed climbing robots. Realizing the transitions by an using under-actuated system without complex control is another contribution of this research. The robot is driven using a tread-wheel mechanism made of a flat sticky polymer to realize fast and robust climbing. Directional compliant joints are used between the two modules to increase the preload on each front wheel. An active tail is used at the end of the second module to compensate for the negative effects of the compliant joint forces. This combination of directional compliant joints and active tail also allows the robot to perform various internal and external transitions passively. The induced positive preload on the front wheels are analyzed and verified. Three types of internal transition and three types of external transition including a thin-wall transition are achieved by the robot prototype. The concept of the directional compliance with the active tail can be adopted to other climbing robots to enhance robustness and mobility.

In this paper, we propose a compliant and tetherless magnetic capsule endoscopic robot. The proposed capsule robot has two key features. First, it has one extra degree of freedom axial contraction capability to perform additional tasks such as a drug releasing, a drug injection, or a biopsy. Also, design features of the magnetically deformed capsule robot are introduced. Its characteristic deformation curve, which was measured using an indentation setup, presents not only the deformation behavior of the magnetic capsule robot but also considerations in the capsule design process. Next, by implementing a magnetically actuated rolling locomotion scheme, the capsule can be controlled externally using a permanent magnet. The proposed magnetic capsule robot is anchored on a tissue wall by the magnetic attraction and rotated by a magnetic torque. This behavior allows a stable locomotion of the magnetic capsule robot and its orientation is controllable during locomotion. To verify the feasibility of proposed locomotion method and the compliant capsule's shape deformation, the magnetic capsule robot was actuated in a synthetic stomach model. The experimental results show that locomotion behavior of the capsule is stable and a successful tracking performance of the proposed magnetic actuation method; average distance gap between the capsule and the external magnet was only 20% of the capsule's body length. Such a soft and tetherless capsule robot can potentially enable minimally invasive diagnostic and treatment applications for stomach diseases.

In this work we develop a stochastic dynamic model of bacteria propelled spherical micro-robots. S. marcescens type bacteria attach in small numbers to the surfaces of spherical microbeads. Given a small number of attached bacteria, generally 8-41, collective-behavior stochastic models become not applicable, hence a model based on individual bacterium behavior and motion is developed. This stochastic simulation is used to study the flexibility of the flagellar hook by comparing simulated and experimental results. The effect of bead diameter and the number of attached bacteria is investigated in this manner, with the results favoring a stiffer flagellar hook. The theoretical framework is intended to be used as a simulation and design tool for bacteria propelled micro-robots employed in future medical applications.

This work introduces new strategies for fluid-based manipulation of micro-scale objects using rotating magnetic micro-robots at low Reynolds numbers. By rapidly spinning the micro-robots, rotational fluid flow is induced which acts to move the micro-objects by fluidic drag. Acting in parallel, teams of these micro-robots are shown to work together to rapidly move micro-objects along planned “virtual channel”s to goal positions. As the micro-robots are themselves highly mobile, the manipulation trajectories are controlled to achieve accurate, fast manipulation of multiple micro-objects in 2-D environments. Experiments are performed in a viscous oil (50 cSt) to simulate the physics of micro-robots which are small enough to fit through small micro-fluidic channels or blood capillaries. The micro-robot and micro-object motions are characterized to support the proposed strategies. Spherical micro-robots 380µm in diameter are used to manipulate 200µm diameter particles with controllable speeds of up to 3.5 mm/s.

Flagellated bacteria have been well understood in regards to its adhesion to surfaces and in swimming propulsion. However, its ability to be used as a source of propulsion for artificial microsystems is of great interest to the micro-robotics community; its high efficiency in converting chemical energy to motion is highly attractive for microsystems that demand a low payload and high rate of actuation. In this paper, we describe the behavior of Serratia marcescens bacteria-propelled polystyrene beads in the presence of a chemoattractant, L-threonine. We compare the results of this chemotactic behavior to that bacteria-propelled bead without a chemoattractant. The results from this analysis indicate a clear sign of directionality, as well as an improved bead velocity, for the bacteria-attached microbeads in the presence of a chemoattractant.

We propose a method to increase propulsion of a micro-scale swimming robot powered by an artificial flagellum through the use of multiple helices while retaining the simple actuation method of a single rotation axis. Scaled up experiments with similar Reynolds number are carried out to compare the performance of five different propulsion designs with pairs of stiff or flexible flagella. The designs feature stiff helices, straight flexible rods, and flexible helices inspired by bacterial flagella. Results indicate that for a given rotation frequency, thrust is proportional to the number of helices, but that the torque required to drive a flagellum offset from the common rotation axis is increased. Furthermore, shape deformation of flexible helices due to bending forces can positively affect thrust under certain conditions. Therefore, given the ease of fabrication, the use of multiple offset flexible flagella is a potential method to achieve increased thrust force in artificial bacteria flagella.

Focusing on the physical interaction between people and machines within safety constraints in versatile situations, this paper proposes a new, efficient actuation approach, continuous-state coupled elastic actuation (CCEA), to provide oncoming human-machine systems with an intrinsic programmable stiffness capacity to shape output force corresponding to the deviation between human motions and set positions of the system. As one of all the possible CCEA systems, a prototype of a 2-DOF coupled elastic actuator is designed to provide a compromise between performance and safety. Using a pair of antagonistic four-bar linkages, the inherent stiffness of the system can be adjusted dynamically. Compared to the state-of-the-art variable stiffness actuators, the CCEA system is unique in that it can achieve near zero mechanical stiffness in an efficient way. In addition, a human-robot interaction model is built to investigate the controlled bandwidth and safety of the CCEA system. For the application of assistive exercises, this study also proposes two kinds of controls for assistive exercises. Finally, a CCEA exoskeleton is built for elbow rehabilitation. Both simulations and experiments are conducted to show some desired properties of the proposed CCEA system.

This paper presents analysis and results for a small and agile wall climbing robot's ability to regain lost adhesion due to degradation of dry fibrillar adhesives. To regain the lost adhesion, two feet are set to the surface and the robot performs a rocking motion on the side where the adhesion has dropped below a safety threshold. The rocking motion applies normal forces to preload the front and rear feet without letting the other foot detach from the surface by alternating the direction of the motor and only allowing small rotation of the leg. Experimental results show that the rocking motion is successful in regaining lost adhesion while using dry fibrillar adhesives on a smooth, vertical acrylic surface. The performance of the fibers over time limits the adhesion that can possibly be mechanically regained and as a result the fibers are over-designed, which gives rise to the need for a power efficient peeling mechanism. The peeling mechanism uses a conditionally locked ankle, implemented with magnets, and a slot to allow the axle to change a pulling force normal to the surface to be a pulling force perpendicular to the surface, which peels the fibers using the uneven loading. Experimental results illustrate that a passive peeling mechanism is successful in reducing the required power to peel. The presented advancements can be applied to other climbing robots using adhesives to allow for safer, more efficient climbing.

Water strider insects have attracted many researchers' attention with their power efficient and agile water surface locomotion. This study proposes a new water strider insect inspired robot, called STRIDE II, which uses new circular footpads for high lift, stability, payload capability, and a new elliptical leg rotation mechanism for more efficient water surface propulsion. The lift, drag and propulsion forces and the energy efficiency of this robot are modeled and experiments are conducted to verify these models. A maximum lift capacity of 53 grams is achieved with a total of 12 footpads, each 4.2 cm in diameter for a robot weighing 21.75 grams. For this robot, a propulsion efficiency of 22.3% is measured. Maximum forward and turning speeds of the robot are measured as 71.5 mm/sec and 0.21 rad/sec, respectively. These water strider robots could be used in water surface monitoring, cleaning, and analysis in lakes, dams, rivers and sea.

Flapping wing micro-aerial vehicles (MAVs) hold great potential for matching the agility of flies, their source of inspiration. At small scales, however, it becomes difficult to balance design mechanical complexity and the weight/lift ratio. Considering control in the initial stages of vehicle design can help define system feasibility and the consequences of making design simplifications. Here, four design alternatives based on a piezoelectric driven passive pitch reversal wing are modeled and compared based on their performance under an ideal linear quadratic regulator (LQR) control scheme. State error over straight line, circular, and cube trajectories are used as a means of comparison. Wing lift and reasonable control input bounds are defined for each design variation. While not nearly as maneuverable as flies, these designs show promise as feasible controllable vehicles.

In this paper, flat elastomers are proposed as an attachment material for climbing robots on less than a few micrometer-scale rough surfaces due to their energy-efficient, quiet, and residue-free characteristics. The proper elastomer is chosen by the use of the current adhesion, friction, and peeling elastomer-contact-mechanics models. Then, adhesion and friction properties of the chosen dry flat-elastomer thick films (Vytaflex-10) are characterized on acrylic and smooth and rough glass surfaces for variations in preloads, speeds, contact times, and elastomer thicknesses. A climbing robot with four-bar-based legged-body kinematics is designed and fabricated as simple and lightweight as possible to demonstrate the feasibility of the elastomers as attachment materials on relatively smooth surfaces. The robot utilizes a passive alignment system to make the footpads parallel to the surface on light contact, a peeling mechanism to minimize the detachment vibration, and a passive tail to minimize the pitch-back moment. Experimental results showed that the robot can climb stably on vertical, smooth surfaces in any direction and can walk inverted for a limited amount of time.

In recent years, flagellar motors of bacteria have not only inspired design of an entirely new category of microrobots, they have also been interfaced with synthetic components and used for controlled actuation of microscale objects. The ultimate goal of these efforts is to develop bio-hybrid swimming micro-robots which use bacteria for actuation, control, and sensing. As bacteria begin to become an integral part of microscale engineered systems, there is a great need for characterizing their performance and understanding the forces involved in interfacing them with synthetic components. In this work repeatability and endurance (performance as a function of time) of an ensemble of bacteria used for actuation of 10 mum polystyrene micro-beads are characterized. Moreover, a series of adhesion assay methods are introduced and used to determine the strength and timeline of adhesion of Serratia marcescens (S. marcescens) bacteria to hydrophobic and hydrophilic polystyrene surfaces.

This video presents a palm-size climbing robot which uses synthetic fibrillar dry adhesives inspired by geckos. With fibrillar footpads, the robot is shown to climb smooth surfaces such as glass and acrylic, and surfaces with micron-scale roughness such as wood. In particular, the agility of the robot is highlighted by demonstrations of climbing, steering, and plane-to-plane transitions.

Atomic force microscope (AFM) based nanomanipulation systems are generally slow, not repeatable and imprecise due to a lack of control on the success of limited attempts in the literature. To improve the amount of control, reliability and precision of such systems, this work proposes an automated nanomanipulation method. Spherical gold nanoparticles with 100 nm diameter are positioned mechanically on a flat mica substrate by contact manipulation by the AFM probe tip to a desired position autonomously. The most significant issue of the manipulation operation is the lack of real-time visual feedback. This issue is solved by developing a robust algorithm for particle center detection and using the AFM cantilever deflection (force) signals to detect contact losses in real-time and to repeat the manipulation again until the target location is reached. Using these solutions, an automated AFM manipulation system is developed and a statistical study is made, where gold nanoparticles are positioned for 50 times to random target positions in different directions and pushing distances. 86% of all the particles could be successfully positioned to the target positions with an accuracy less than 100 nm. Unsuccessful positioning operations are due to the particle sticking to either the tip (8%) or the substrate (6%). Additionally, performance of the successful manipulations are investigated on 60 manipulation operations in 12 different directions and 5 different distances. The metrics used to quantify performance are the final particle position error and the average manipulation speed.

A quadrupedal robot inspired by the basilisk lizard was developed and modeled with a 3D real time simulation. Due to the robot's geometry, leg motion, and water interactions, the net pitch moment at the center of mass is not zero making pitch motion unstable. This paper introduces two types of tails, passive and active, to stabilize pitch motion and analyzes the advantages and disadvantages of each. It is shown in simulation that a purely passive tail can stabilize pitch motion and lead to a steady state robot pitch angle in the absence of disturbances. It is further shown that an active tail can compensate for disturbances and correct any drift in the robot body pitch angle due to changes in robot running speed.

In this paper, the design, analysis, and development of a sixteen-legged palm-sized climbing robot using flat bulk tacky elastomer adhesives as an attachment method is presented. A legged robot with four-bar based kinematics is designed and fabricated with elastomeric footpads. The proposed robot has a passive peeling mechanism for energy efficient and vibration free detachment. A rocker-type mechanism in the leg and compliant foam under the footpads are utilized for passive alignment on concave and convex surfaces. Adhesion experimental data is used to estimate the adhesion and preload saturation on the footpads on different angled acrylic surface. It is showed that although the initial preload does not affect the adhesion and preload saturation point, the orientation and the weight of the robot, roughness of the surface, and waiting time between consecutive steps greatly effect the climbing performance. Experimental results revealed that the robot can climb in any direction in 3D space on smooth surfaces, such as acrylic and glass. It can carry a payload of up to 2 N, which is almost twice as its own weight, on a smooth inverted surface. The robot can robustly climb vertically on relatively rough surfaces such as a painted wall or a wooden door. Potential applications of this robot include inspection, exploration, maintenance, cleaning, repair, and search and rescue.

Tankbot is a miniature, energy efficient, lightweight (60 g), and robust climbing robot. It uses the continuous detachment force (peeling) of the flat, bulk tacky elastomer tread to climb. An optimum peeling angle with a preliminary analysis of the pretension effect, and the tread force distributions are presented. A passive tail transfers the peeling force from the rear wheel to the front and ensures intimate continuous contact with the surface. Tankbot works in any orientation on smooth surfaces, such as glass and acrylic, of all slope angles (0 – 360 degrees). However, the robot can only work vertically on relatively rough surfaces in any direction, such as wood, metal, painted wall, and painted brick. Tankbot can carry a payload of up to 40 g and 100 g on inverted and vertical surfaces, respectively. In addition, the robot can go over obstacles up to 15 mm tall on smooth vertical surfaces. Internal transitioning from horizontal to vertical and vertical to horizontal and external transitioning from vertical to the horizontal are also achieved. The potential applications of this robot include inspection, exploration, maintenance, cleaning, repair, and search and rescue.

To improve on current methods of minimally invasive surgery, research is being carried out on systems that will permit procedures to be conducted on the micro-scale using remotely operated micro-robots. One of the major stumbling blocks to meeting this need has been the absence of a practical micromotor with a volume of less than 1 mm3with which to drive these devices. To rectify this, we present a piezoelectric ultrasonic resonant micromotor with a volume of approximately 0.75 mm3. The motor uses a novel helically cut stator that matches axial and torsional resonant frequencies, excited by a lead zirconate titanate element 0.03 mm3in volume. An earlier motor using the same stator design, but a larger overall volume, achieved a start-up torque of 47 nNm and no load angular velocity of 830 rad/s. This performance is on the order necessary to propel a swimming microbot in small human veins.

This work presents the control of multiple untethered rectilinear magnetic micro-robots (Mag-¿Bots) with dimensions 250 × 130 × 100 ¿m3actuated by pulsed external magnetic fields, which translate by induced stick-slip motion at speeds of up to 4 mm/s immersed in silicone oil. Multiple Mag-¿Bot control is enabled by employing an array of individually addressable electrostatic surfaces to selectively anchor individual Mag-¿Bots. Coupled parallel and uncoupled serial motion of multiple robots is demonstrated, and they can combine to form an assembly that is also capable of motion. Manipulation of 230 ¿m diameter microspheres is also demonstrated cooperatively by two Mag-¿Bots in a fluid environment, and is enhanced when the two Mag-¿Bots are combined. An analysis of the electrostatic anchoring forces and the forces relevant to manipulation is discussed.

A quadrupedal water runner robot inspired by the basilisk lizard has previously demonstrated the capability of water surface locomotion. Since the robot is aimed for the amphibious locomotion, a compatible design on both ground and water surface is discussed in this paper. A compliant footpad which can transfer elastic energy to propulsive momentum is introduced and modeled using a pseudo-rigid-body model. Dynamic modeling of the footpad and the robot provides a criterion of efficient ground locomotion. For the water surface locomotion, drag force can be reduced by compliance of the footpad. The optimized design taking into account two locomotions is studied and analyzed for stability using the Poincare map.

This paper presents the manipulation of microspheres under water by use of an untethered electromagnetically actuated magnetic microrobot (Mag-muBot), with dimensions 250 times 130 times 100 mum3. Manipulation is achieved by two means: contact and noncontact pushing modes. In contact manipulation, the Mag-muBot is used to physically push the microspheres. In noncontact manipulation, the fluid flow generated by the translation of the Mag-muBot is used to push the microspheres. Modeling of the system is performed, taking into account micrometer-scale surface forces and fluid drag effects to determine the motion of a sphere within a robot-generated fluid flow. Fluid drag models for free-stream flow and formulations for near-wall flow are both analyzed and compared with the experiments, in which pushing of two sphere sizes, i.e., 50 and 230 mum diameters, is characterized in a controlled, robot-generated flow. Dynamic simulations are provided using the developed physical models to capture this behavior. We find that the near-wall physical models are, in general, in agreement with the experiment, and free-stream models overestimate microsphere motion.

This paper presents the fabrication, characterization and testing of bio-inspired synthetic dry adhesive fiber arrays. Fibers were fabricated via micromolding followed by spatula tip formation via dipping. Arrays of fibers with diameters between 28 mum and 57 mum and a height of 114 mum were fabricated with high uniformity on 6.25 cm2areas with up to 95% yield. Adaptation to uneven surfaces was observed with fiber elongations over 6 times the original height of the fiber. The unstructured sample exhibited 1.6 times as much adhesion as the fiber array sample for the flat punch indenter. However, fibrillar samples demonstrated up to 5.3 times as much adhesion as the unstructured sample for the hemispherical indenter. The fibrillar adhesive sample was implemented on a wall climbing robot which was able to carry itself and climb a distance on a painted wall and wood door.

The water runner robot is designed to run on the surface of water in a manner similar to the basilisk lizard. To do so, it must generate a lift force greater than its weight by slapping and stroking its foot through the water, creating an air cavity in the process. In addition, it must remove its foot before this cavity collapses. Basilisk lizards deal with this problem by folding their feet during retraction from the air cavity to avoid prematurely collapsing the cavity and generating excess drag. Several different passive foot designs for the water runner were analyzed to determine which had the largest lift and created the least amount of drag. Feet with folding sections which collapse during retraction and spring back into place once the foot has exited the water were found to work best. Those feet which allowed air to pass through during retraction provided the least net lift. Elliptic feet with their major axis in line with the direction of running performed better than simple circular feet. Consequences of these results are discussed.

This work presents an untethered magnetic micro- robot with dimensions of 250mumx 130mumx 100mum. The robot is composed entirely of neodymium-iron-boron fabricated using laser micro-machining. It is actuated by a system of five macro-scale electromagnets. By using electromagnets to control the robot, the surface on which the robot operates need not be specialized, smooth, patterned, nor conductive. Two control methods, both based on periodic excitation of the robot, are attempted and compared. Controllable motion at speeds in excess of 2.8 mm/s, approximately 11 body lengths per second, is demonstrated. Teleoperated motion in two dimensions is shown, and the assembly of micro-particles is demonstrated underwater. Potential future applications include micro-scale manipulation, fabrication, and assembly of micro-systems.

One of many difficulties in creating flapping wing miniature robotic aerial vehicles lies in generating proper wing trajectory that would result in sufficient lift forces for hovering and maneuvering. A completely passive wing pitch reversal design based on the wingpsilas inertial dynamics is proposed. Dynamics are simulated using a Lagrangian formulation, resulting in theoretical predictions for aerodynamic forces and motion trajectory. Based on the generated wing lift and rotation trajectory delay, the wingpsilas sensitivity to variations in spring stiffness, damping coefficient, driving frequency, and rotation axis position is analyzed and the above parameters are evaluated for efficiency as control inputs. Furthermore, a wing control methodology based on slow actuation of spring stiffness and flapping frequency is proposed, allowing for partial position/orientation of the robot in free space.

This paper proposes a 3-D dynamic simulation of a previously developed basilisk lizard inspired quadruped robot, which is capable of locomotion on the surface of water. Using this 3-D simulation along with several 1-D and 2-D models, stability in terms of robot elevation from the water surface and robot rolling are examined. Analysis of the lifting force shows the robot is capable of running on water using viscous drag forces. Using this analysis, a criterion for convergence to a steady state distance from the water is presented. It is determined that 7-12 Hz is an appropriate running frequency range for the robot to lift its weight. Compliant footpads are found to be beneficial in reducing the force associated with pulling out of the water. Further, from the roll motion analysis, previous designs result in instability along the roll axis. By comparing leg running frequency to the bodypsilas roll frequency, the minimum required roll moment of inertia for stable roll motion can be determined.

This paper describes the design and development of a novel robot, which attempts to emulate the basilisk lizard's ability to run on the surface of water. Previous studies of the lizards themselves have characterized their means of staying afloat. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180degphase shift to achieve locomotion on the water's surface. Simulations for determining robot lift and power requirements are presented. Through simulation and experimentation, parameters are varied with the focus being a maximization of the ratio of lift to power. Four legged robots were more easily stabilized, and had a higher lift-to-power ratio than two legged robots. Decreases in characteristic length and running speed, and increases in foot diameter and foot penetration depth all cause a higher lift to power ratio. Experimental lift approached 80 gr, and experimental performance exceeded 12 gr/W for four legged robots with circular feet. This work opens the door for legged robots to become ambulatory over both land and water, and represents a first step toward robots which run on the water instead of floating or swimming.

In this paper, a strategy for controlled pushing is presented for microassembly of 4.5 mum polystyrene particles on a flat glass substrate using an atomic force microscope probe tip. Real-time vision based feedback from a CCD camera mounted to a high resolution optical microscope is used to track particle positions relative to the tip and target position. Tip-particle system is modeled in 2D as a nonholonomic differential drive robot. Effectiveness of the controller is demonstrated through experiments performed using a single goal position as well as linking a series of target positions to form a single complex trajectory. Cell decomposition and wavefront expansion algorithms are implemented to autonomously locate a navigable path to a specified target position. Control strategy alleviates problem of slipping and spinning during pushing.

A microrobotic method for fabricating multilayered poly(lactic acid) (PLA) biological scaffolds using micropipettes for tissue engineering applications is presented. Biological scaffolds are fabricated over several different substrates by drawing and solidification of a viscous liquid polymer solution pumped continuously through a glass micropipette. The proposed method produces highly aligned, multilayered, crisscrossed fiber scaffolds with user specified pore sizes and diameters in the range from 1 to 10 micrometer. Attachment, proliferation and differentiation of C2C12 mouse pluripotential cells seeded on individual, parallel, and intersecting fibers is successfully demonstrated. The proposed robotic methodology consistently provides parameterized biological scaffolds to aid studies in tissue engineering and to develop novel MEMS, filtration and controlled drug delivery devices

Recently, a few water strider robots that mimic the static and dynamic key characteristics of the insect water striders have been reported in the literature. These robots either lacked mobility or was tethered to an external source of power. Using the recent findings on the supporting legs of these robots creating repulsive surface tension based lift forces, a heavier yet highly maneuverable and non-tethered water strider robot, called STRIDE, is proposed in this paper. STRIDE uses two miniature DC motors and a lithium-polymer battery that are connected to the driving circuit on-board. Optimal leg shape is manufactured by bending 0.33 mm diameter stainless steel wires with a Teflonreg coating. This 6.13 gr non-tethered robot with twelve supporting legs demonstrated a linear motion of 8.7 cm/s and a rotational motion of 0.8 rad/s. STRIDE would have potential applications in continuous water quality monitoring on lakes, dams, and other water sources and in entertainment and education in the near future.

In this work, teleoperated nanomanipulation with force feedback is demonstrated by using an atomic force microscope on the slave side and a haptic device on the master side. Three main topics are addressed that are especially relevant for teleoperation at these scales: transparency, impedance reflection according to human perception, and stability. The proposed passivity based bilateral control scheme provides a stable means of teleoperation with an adaptive force scaling factor according to impedance limits that can be set by the operator and as transparent as possible. As a result, a robust platform to perform teleoperated nanomanipulation on a broad range of materials is achieved. Performance of the resulting bilateral controller is demonstrated in experimental results for simple vertical nanomanipulation touching experiments on glass and polydimethylsiloxane substrates.

Recent biological studies on water strider insects revealed how they maintain stability and maneuver on the surface of water. While macroscale bodies use buoyancy, these very small insects use surface tension force to balance their weight on water. This paper proposes a biologically inspired miniature robot that utilizes the unique scaling advantage of these insects. The paper focuses on understanding the physics of the interaction between the insect and the surface of water and on designing a robot that mimics their key features. Hydrophobic Teflon coated wire legs optimized to take the most advantage of the surface tension force are used to support the weight of the 1-g robot. It is shown that twelve of these legs can support up to 9.3 g of payload. A T-shape actuation mechanism with three piezoelectric unimorph actuators is designed and studied to enable controlled locomotion. Static and dynamic properties of the robot are analyzed and compared with the experimental results. The tethered robot can successfully make both linear and rotational motions. Maximum forward speed is measured to be 3 cm/s, and the rotational speed is 0.5 rad/s. This robot proposes a new way of locomotion on water surface for future robots and devices.

Recent studies on the insect water strider showed that the insect heavily relies on surface tension force to stay afloat. Inspired by this insect, water strider robots have been developed using the same locomotive principles as the insect. This paper focuses on numerically modeling the supporting legs of the insect and the robots. The rigid-leg model as well as the compliant-leg model is developed using numerical approaches, under an assumption made on the water surface breaking condition. The effect of different leg material and geometry are discussed. It is shown through simulations that four 7 cm-long Teflonreg coated compliant supporting legs with optimized shapes can lift up to 4.3 grams (0.15 g/cm), while an actual prototype carried 3.7 grams. Another prototype using twelve of these legs successfully lifted 9.3 grams. Experiments show that the analyses capture the important features of the supporting legs. The design rules proposed in this paper are useful in understanding the insect statics and also the robotic water strider supporting leg design. This study allows a heavier robot to be used for education, entertainment or environment monitoring purposes

In this paper, force-controlled microcontact printing using microassembly-based particle templates is investigated. Polystyrene microparticles are assembled semi-automatically into a desired pattern on a glass substrate using an atomic force microscope nanoprobe installed on a nanopositioning stage. The micropattern on glass is sputtered with aluminum and removed of microparticles by ultrasonic vibration, resulting in a template with microfeatures corresponding to the microparticles. A soft lithography method is used to mold elastomeric polymers on the template, resulting in a stamp. The stamp is inked and printed using a force-controlled system onto a polystyrene substrate. Depending on the particle size and contact force, a smaller micro to nanometer sized pattern can be formed. As the spherical patterns on the stamp collapse due to interfacial contact forces, force-controlled microcontact printing is crucial for controlling the size of stamped features. Green fluorescent protein is used as the ink, enabling the use of fluorescent imaging to observe the stamped imprints. Preliminary experiments using 4.5 and 10 mum diameter polystyrene particles shows the feasibility of our technique. Thus it is possible to realize micro/nanopatterns using assembled microparticle-based stamps in high volumes

In this paper, the design, analysis, and fabrication of a gecko-inspired climbing robot are discussed. The robot has kinematics similar to a gecko's climbing gait. It uses peeling and steering mechanisms and an active tail for robust and agile climbing as a novelty. The advantage of this legged robot is that it can explore irregular terrains more robustly. Novel peeling mechanism of the elastomer adhesive pads, as well as steering and stable climbing using an active tail are explored. The design, fabrication, analysis and test of the robot are reported. Experimental results of walking and climbing up to 85deg sloped acrylic surfaces as well as successful steering and peeling mechanism tests are demonstrated. The potential applications foreseen for this kind of robots are inspection, repair, cleaning, and exploration

This paper introduces a novel robot which can run on the surface of water in a manner similar to basilisk lizards. Previous studies on the lizards themselves have characterized their method of propulsion and their means of staying afloat. By slapping and stroking their feet into the water, the lizard effects a momentum transfer which provides both forward thrust and lift. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180deg phase shift to achieve bipedal locomotion on the water's surface. Computational and experimental results are presented and reviewed with the focus being a maximization of the lift to power ratio. After optimization, two legged models can experimentally provide 12-15 g/W of lift while four legged models can provide 50 g/W of lift. This work opens the door for bipedal and quadrupedal robots to become ambulatory over both land and water, and represents a first step toward studies in amphibious stride patterns; step motions equally conducive to propulsion on water and land

This paper proposes a small-scale agile wall climbing robot able to navigate on smooth surfaces of any orientation, including vertical and inverted surfaces, which uses adhesive elastomer materials for attachment. Using two actuated legs with rotary motion and two passive revolute joints at each foot the robot can climb and steer in any orientation. Due to its compact design, a high degree of miniaturization is possible. It has onboard power, sensing, computing, and wireless communication which allow for semi-autonomous operation. Various aspects of a functioning prototype design and performance are discussed in detail, including leg and feet design and gait control. The current prototype can climb 90deg slopes at a speed of 6 cm/s and steer to any angle. This robot is intended for inspection and surveillance applications and, ultimately, space missions

In a haptic interface system with a nanoscale virtual environment (NVE) using an atomic force microscope, not only is stability important, but task-based performance (or fidelity) is crucial. In this paper, we introduce a nanoscale virtual coupling (NSVC) concept and explicitly derive the relationship between performance, stability, and scaling factors of velocity (or position) and force. An available scaling factor region is represented based on Llewellyn's absolute stability criteria and the physical limitation of the haptic device. For the stable haptic interface, the sampled time passivity controller is implemented in the NVE. Experiments have been performed for telenanomanipulation tasks, such as positioning, indenting, and nanolithography with guaranteed stability in the NVE. Note to Practitioners-This paper suggests methods and control schemes for the task-based and stable telenanomanipulation in the nanoscale virtual environment (NVE). The proposed task-based and stable telenanomanipulation in the NVE can be used for an augmented human machine interface for the manipulation of nanoscale objects with the atomic force microscope (AFM). In addition, it is beneficial for learning or performing nanoscale tasks, such as nanolithography, nanoindenting, nanofabrication, and cell manipulation. Also, the interaction with the NVE using haptic device provides a useful tool for researchers in a variety of disciplines, such as biology, chemistry, and physics. Moreover, it may even be applied to educational purposes. In future research, the developed stable haptic interface would be integrated with the AFM system as a slave manipulator for telenanomanipulation experiments, such as pushing a nanoparticle with precise positioning and nanoassembly.

Climbing robots can perform many tasks inaccessible to other robots or humans such as inspection, repair, cleaning, surveillance, and exploration. This paper presents and discusses the design, fabrication, and evaluation of two novel bio-inspired climbing robots. Both are inspired by the locomotion of Geckos, a highly skilled natural climber. They are developed for terrestrial and extra-terrestrial environments, and their kinematics is inspired by the Geckos’ gait. The first relatively large robot actuated by conventional motors is designed to operate at both in Earth and space scenarios. The second robot, whose motion is controlled using shape memory alloy actuators and size can be miniaturized to few centimeters scale, is designed for terrestrial applications. Preliminary prototypes of these robots are developed, demonstrated, and evaluated by steep and flat acrylic surface climbing tests. Current robots can successfully climb up to 65 ° slopes at 2 cm/sec speeds.

We propose a demonstration of extremely scalable modular robotics algorithms developed as part of the Claytronics Project (http://www-2.cs.cmu.edu/~claytronics/), as well as a demonstration of proof-of-concept prototypes. Our effort envisions multi-million-module robot ensembles able to morph into three-dimensional scenes, eventually with sufficient fidelity so as to convince a human observer the scenes are real. Although this work is potentially revolutionary in the sense that it holds out the possibility of radically altering the relationship between computation, humans, and the physical world, many of the research questions involved are similar in flavor to more mainstream systems research, albeit larger in scale. For instance, as in sensor networks, each robot will incorporate sensing, computation, and communications components. However, unlike most sensor networks each robot will also include mechanisms for actuation and motion. Many of the key challenges in this project involve coordination and communication of sensing and actuation across such large ensembles of independent units.

Besides imaging and characterization, proximal probes are proposed to be use as a three-dimensional (3D) nanoscale manipulation and manufacturing tool In this work. We propose 3D nanoscale pulling of liquid polymer micro/nanofibers by precise positioning of atomic force microscope (AFM) nanoprobes and control of polymer solidification. An AFM probe is used to pull or extrude thermoset or thermoplastic polymers precisely to fabricate 3D polymer micro/nano-fiber structures. A liquid polymer fiber bridge between the probe tip and a substrate is maintained when pulling the probe from the surface with controlled speed and position. We present results of our pulling experiments in vertical, horizontal and arbitrary 3D pulling directions for PMMA polymer fibers. Implications and future directions are discussed. This micro/nano-fiber pulling technology would have wide applications in nano-circuit interconnects, prototyping novel nano-electronic devices, 3D polymer fiber based nano-actuators, photonic devices, and novel smart sensors and materials.

This paper proposes techniques to fabricate synthetic gecko foot-hairs for future wall-climbing robots, and models for understanding the synthetic hair design issues. Two nanomolding fabrication techniques are proposed: the first method uses nanoprobe indented flat wax surface and the second one uses a nano-pore membrane as a template. These templates are molded with silicone rubber, polyimide, etc. type of polymer under vacuum. Next, design parameters such as length, diameter, stiffness, density, and orientation of hairs are determined for non matting and rough surface adaptability. Preliminary nano-hair prototypes showed adhesion close to the predicted values for natural specimens.

A surgical micro-robot that swims inside the human ureter is proposed to provide a novel and minimally invasive method of kidney stone destruction. Inspired by the swimming mechanisms of bacteria such as E. coli, the robot utilizes biomimetic synthetic flagella composed of multiwalled carbon nanotubes that are driven into a rotating helical shape by a micro motor. Design aspects are discussed with the focus on locomotion. The performance of the propulsion mechanism is determined through simultaneous modeling of the viscous drag on the filaments and the stress strain behavior of the nanotubes. The effects of the synthetic flagellum geometry and frequency of rotation on efficiency and swimming speed are explored. With 1 nW of power, utilizing 100 /spl mu/m-long filaments, swimming speeds approaching 1 mm/s are shown to be possible for a realistic design. The proposed new robot would revolutionize kidney stone destruction if implemented, yet the design of the robot and the propulsion analysis are applicable to many other possible surgical procedures.

A four-bar mechanism with two flexible links is proposed to be used in a micromechanical flying insect robot wing thorax design for stroke amplification. PZT-5H and PZN-PT based unimorph actuators are utilized at the input link of the four-bar. The kinematics and dynamics of the proposed wing structure with two parallel four-bar mechanisms are analyzed, and DC forces generated at the wing are computed for checking the feasibility of the design. Using laser micromachining and folding techniques, prototype four-bars are constructed, and it is shown that the single four-bar structure can have 90-100/spl deg/ stroke motion at 29 Hz with a rigid polyester wing on it.

A human-machine interface is proposed for teleoperated nano scale object interaction and manipulation. Design specifications for a bilateral scaled teleoperation system with slave and master robots, sensors, actuators, and control are discussed. Phantom and home-made haptic devices are utilized as the master manipulator, and a piezoresistive MEMS fabricated probe is selected as the slave manipulator, and topology and force sensor. A force reflecting servo type teleoperation control is chosen, and initial experiments are realized for interacting with silicon surfaces and nano structures. It is shown that fine structures can be felt on the operator's finger successfully.

This paper focuses on the design, fabrication and characterization of unimorph actuators for a microaerial flapping mechanism. PZT-SH and PZN-PT are investigated as piezoelectric layers in the unimorph actuators. Design issues for microaerial flapping actuators are discussed, and criteria for the optimal dimensions of actuators are determined. For low power consumption actuation, a square wave based electronic driving circuit is proposed. Fabricated piezoelectric unimorphs are characterized by an optical measurement system in quasi-static and dynamic mode. Experimental performance of PZT-5H and PZIV-PT based unimorphs is compared with desired design specifications. A 1-DOF flapping mechanism with a PZT-SH unimorph is constructed, and 180/spl deg/ stroke motion at 95 Hz is achieved. Thus, it is shown that unimorphs could be promising flapping mechanism actuators.

Considers a 2 DOF resonant thorax structure signed and fabricated for the MFI project. Miniature piezoelectric PZN-PT unimorph actuators were fabricated and used to drive a four-bar transmission mechanism. The current thorax design utilizes two actuated four-bars and a spherical joint to drive a rigid wing. Rotationally compliant flexure joints have been tested with lifetimes over 10/sup 6/ cycles. Wing spars were instrumented with strain gauges for force measurement and closed-loop wing control.

Flapping wings provide unmatched manoeuvrability for flying microrobots. Recent advances in modelling insect aerodynamics show that adequate wing rotation at the end of the stroke is essential for generating adequate flight forces. We developed a thorax structure using four bar frames combined with an extensible fan-fold wing to provide adequate wing stroke and rotation. Flow measurements on a scale model of the beating wing show promising aerodynamics. Calculations using a simple resonant mechanical circuit model show that piezoelectric actuators can generate sufficient power, force and stroke to drive the wings at 150 Hz.

In this paper, a fine particle positioning system using a piezoresistive cantilever, which is normally utilized in atomic force microscopy, as the manipulator is proposed. Modeling and control of the interaction forces among the manipulator, particle and surface have been realized for moving particles with sizes less than 3 /spl mu/m on a Si substrate in 2D. Optical microscope (OM) is utilized as the vision sensor, and the cantilever behaves also as a force sensor which enables contact detection and surface alignment sensing. A 2D OM real-time image feedback constitutes the main user interface, where the operator uses mouse cursor and keyboard for defining the task for the cantilever motion controller. Particle manipulation experiments are realized for 2.02 /spl mu/m goal-coated latex particles, and it is shown that the system can be utilized in 2D micro-particle assembling.

In this paper, a teleoperated micro/nano scale touching system is proposed, and micro/nano contact mechanics models are introduced. Using a 1-DOF haptic device, force-reflecting servo type scaled teleoperation controller, and atomic force microscopy cantilever tip, touching experiments and virtual reality simulator for micro/nano-touch are realized. Scaling issue of the micro/nano forces and positions is discussed and possible solutions are proposed. For the first time upon our knowledge, such issue is discussed with nano scale experimental results. Experimental results show that micro/nano contact force feedback can be held for flat surfaces with the proposed system.

A tele-nanorobotics system using an atomic force microscope (AFM) as the nanorobot has been proposed. Modeling and control of the AFM cantilever, and modeling of nanometer scale forces have been realized for telemanipulation applications. Besides 3-D virtual reality visual feedback in the user interface, a 1 DOF haptic device has been constructed for nano scale haptic sensing. For feeling the nano forces, a bilateral teleoperation control system with virtual impedance approach has been introduced. Initial experiments and simulations on the AFM and teleoperation system show that the system can be utilized for different tele-nanomanipulation applications such as 2-D nano particle assembly or biological object manipulation.