Microswimmers are sub-millimeter swimming robots that show potential as a platform for controllable locomotion in applications, including targeted cargo delivery and minimally invasive surgery. To be viable for these target applications, microswimmers will eventually need to be able to navigate environments with dynamic fluid flows and forces. Experimental studies with microswimmers towards this goal are currently rare because of the difficulty of isolating intentional microswimmer locomotion from environment-induced motion. In this work, we present a method for measuring microswimmer locomotion within a complex flow environment using fiducial microspheres. By tracking the particle motion of ferromagnetic and non-magnetic polystyrene fiducial microspheres, we capture the effect of fluid flow and magnetic field gradients on microswimmer trajectories. We then determine the field-driven translation of these microswimmers relative to fluid flow and demonstrate the effectiveness of this method by illustrating the motion of multiple microswimmers through different flows.

Miniaturizing legged robot platforms is challenging due to hardware limitations that constrain the number, power density, and precision of actuators at that size. By leveraging design principles of quasi-passive walking robots at any scale, stable locomotion and steering can be achieved with simple mechanisms and open-loop control. Here, we present the design and control of “Zippy”, the smallest self-contained bipedal walking robot at only 3.6 cm tall. Zippy has rounded feet, a single motor without feedback control, and is capable of turning, skipping, and ascending steps. At its fastest pace, the robot achieves a forward walking speed of 25 cm/s, which is 10 leg lengths per second, the fastest biped robot of any size by that metric. This work explores the design and performance of the robot and compares it to similar dynamic walking robots at larger scales.

As environmental disasters happen more frequently and severely, seeking the source of pollutants or harmful particulates using plume tracking becomes even more important. Plume tracking on small quadrotors would allow these systems to operate around humans and fly in more confined spaces, but can be challenging due to poor sensitivity and long response times from gas sensors that fit on small quadrotors. In this work, we present an approach to complement chemical plume tracking with airflow source-seeking behavior using a custom flow sensor that can sense both airflow magnitude and direction on small quadrotors (< 100 g). We use this sensor to implement a modified version of the ‘Cast and Surge’ algorithm that takes advantage of flow direction sensing to find and navigate towards flow sources. A series of characterization experiments verified that the system can detect airflow while in flight and reorient the quadrotor toward the airflow. Several trials with random starting locations and orientations were used to show that our source-seeking algorithm can reliably find a flow source. This work aims to provide a foundation for future platforms that can use flow sensors in concert with other sensors to enable richer plume tracking data collection and source-seeking.

Understanding airflow around a drone is critical for performing advanced maneuvers while maintaining flight stability. Recent research has worked to understand this flow by employing 2D and 3D flow sensors to measure flow from a single source like wind or the drone’s relative motion. Our current work advances flow detection by introducing a strategy to distinguish between two flow sources applied simultaneously from different directions. By densely packing an array of flow sensors (or whiskers), we alter the path of airflow as it moves through the array. We have named this technique “flow shadowing” because we take advantage of the fact that a downstream whisker shadowed (or occluded) by an upstream whisker receives less incident flow. We show that this relationship is predictable for two whiskers based on the percent of occlusion. We then show that a 2x2 spatial array of whiskers responds asymmetrically when multiple flow sources from different headings are applied to the array. This asymmetry is direction-dependent, allowing us to predict the headings of flow from two different sources, like wind and a drone’s relative motion.

In this work, we present a thin-film shape memory alloy microactuator with a magnetic spring. This novel actuator design utilizes two permanent magnets and 3D-printed magnet holders to effectively apply a tensile strain on the NiTi thin-film. This actuator is expected to generate 8.7 mN of blocking force, and a free displacement of 30 µm is experimentally characterized. The actuator leverages bare NiTi film (∼ 1 µm thick) for actuation, enabling a high actuator bandwidth up to 50 Hz. A comprehensive analytical model is also studied, which was then validated by comparing to the experimental results. A launcher mechanism was designed and integrated with the NiTi actuator, and this mechanism was used to launch a microscale projectile (a salt grain) thereby demonstrating the relative high power actuation achievable with thin-film NiTi.

Whisker-based tactile sensors have the potential to perform fast and accurate 3D mappings of the environment, complementing vision-based methods under conditions of glare, reflection, proximity, and occlusion. However, current algorithms for mapping with whiskers make assumptions about the conditions of contact, and these assumptions are not always valid and can cause significant sensing errors. Here we introduce a new whisker sensing system with a tapered, flexible whisker. The system provides inputs to two separate algorithms for estimating radial contact distance on a whisker. Using a Gradient-Moment (GM) algorithm, we correctly detect contact distance in most cases (within 4% of the whisker length). We introduce the Z-Dissimilarity score as a new metric that quantifies uncertainty in the radial contact distance estimate using both the GM algorithm and a Moment-Force (MF) algorithm that exploits the tapered whisker design. Combining the two algorithms ultimately results in contact distance estimates more robust than either algorithm alone.

Creating microscale actuated mechanisms in 3D space is extremely challenging due to limitations in microfabrication processes. In this work, we present a 3D-printed adaptive microgripper that is driven by thin-film NiTi microactuators with 3D-printed linkage mechanisms. The microgripper's fingers are passively adaptive so that the microgripper can provide conformal gripping on 3D objects. The microgripper can move its fingers by$\mathbf{225}\ \boldsymbol{\mu} \mathbf{m}$and apply a blocking force of$\mathbf{30}\ \boldsymbol{\mu} \mathbf{N}$per one finger when 20 mA was applied to the NiTi actuators. The microgripper was also integrated onto a printed circuit board with a current regulating circuit and a 9 V battery. Since the NiTi actuator requires a low voltage for actuation, the microgripper could be integrated with simple and affordable electronics. The fully integrated microgripper system was demonstrated playing with a shape sorting box at the microscale for the first time.

Flapping wing micro aerial vehicles face challenges in sensing and reacting to disturbances like wind gusts. This work introduces a new microscale bio-inspired digital strain sensor to detect these perturbations. The sensor is designed to change logic states when a specified strain threshold has been reached. The sensors are 3D printed on a flexible Mylar wing using two-photon polymerization. Three digital sensors with varying strain thresholds demonstrate differences in activation timing due to different design parameters. The sensors are tested at the 25 Hz flapping frequency of a hawkmoth, an insect with comparable wing size. A perturbation was added to the flapping wing by subjecting it to a 3 m/s wind gust. A single digital sensor is able to identify the wind disturbance by comparing the time of the first strain threshold crossing. A separate approach looks at the change in sensor ‘on’-time for each flap cycle and provides a clear indication of the wind disturbance.

Robots that use impulsive mechanisms to achieve high-speed and high-powered motion are becoming more common and better understood, but control of these systems remains relatively rudimentary. Among robots that use spring actuation to generate motion, robot actuation and mechanisms are usually not controlled intentionally in order to achieve variation in the system's behavior, or they are controlled only roughly via adjustments made to the amount of energy stored in the mechanism. We describe the development, construction, and test of an impulsive catapult mechanism whose design is inspired by the grasshopper leg and for which extensive variation in the projectile trajectory is achieved by force control of the actuator that restrains the spring. As a step toward future controlled jumping robots, we give a detailed model of this system, validate this model experimentally, and explain how the actuator dynamics are critical to our ability to vary the system's trajectory using this approach. This work represents a novel approach to the control of spring actuated robots and illustrates how they can be controlled even under highly limiting actuator constraints.

We present simplified 2D dynamic models of the 3D, passive dynamic inspired walking gait of a physical quasi-passive walking robot. Quasi-passive walkers are robots that integrate passive walking principles and some form of actuation. Our ultimate goal is to better understand the dynamics of actuated walking in order to create miniature, untethered, bipedal walking robots. At these smaller scales there is limited space and power available, and so in this work we leverage the passive dynamics of walking to reduce the burden on the actuators and controllers. Prior quasi-passive walkers are much larger than our intended scale, have more complicated mechanical designs, and require more precise feedback control and/or learning algorithms. By leveraging the passive 3D dynamics, carefully designing the spherical feet, and changing the actuation scheme, we are able to produce a very simple 3D bipedal walking model that has a total of 5 rigid bodies and a single actuator per leg. Additionally, the model requires no feedback as each actuator is controlled by an open-loop sinusoidal profile. We validate this model in 2D simulations in which we measure the stability properties while varying the leg length/amplitude ratio, the frequency of actuation, and the spherical foot profile. These results are also validated experimentally on a 3D walking robot (15cm leg length) that implements the modeled walking dynamics. Finally, we experimentally investigate the ability to control the heading of the robot by changing the open-loop control parameters of the robot.

Moths use hundreds of strain sensors (campaniform sensilla) on each wing to quickly respond to perturbations that may otherwise destabilize the moth during flight. A similar sensing approach could help stabilize micro-aerial vehicles (MAVs), but large sensor arrays are challenging due to the wiring and large latency that exists when capturing data from many traditional strain sensors. This work introduces a simplified bio-inspired strain sensor; the sensor interface and kinematics were inspired by campaniform sensilla that output a spike only in response to signals of interest. The engineered sensor outputs a discrete analog signal representing strain thresholds. A kinematic model of the sensor design is developed and describes the measured strain in terms of the sensor’s geometric parameters. This model is used to understand trade-offs between sensor resolution and range, and is validated using a finite element model (FEM) of the sensor. The sensor was designed with ease of fabrication in mind, using simple techniques and commercially available components. Fabricated sensors were tested in a four-point flexural test, and the data from the analytical and FEM model show good agreement with the experimental results. The sensors demonstrate resolutions of 83, 158, and 281 microstrain for the different designs tested. A sensor is placed on a model wing to illustrate future applications to MAVs as well as the sensor’s ability to sense both compressive and tensile strains.

This work presents the design, fabrication, and characterization of an airflow sensor inspired by the whiskers of animals. The body of the whisker was replaced with a fin structure in order to increase the air resistance. The fin was suspended by a micro-fabricated spring system at the bottom. A permanent magnet was attached beneath the spring, and the motion of fin was captured by a readily accessible and low- cost 3D magnetic sensor located below the magnet. The sensor system was modeled in terms of the dimension parameters of fin and the spring stiffness, which were optimized to improve the performance of the sensor. The system response was then characterized using a commercial wind tunnel and the results were used for sensor calibration. The sensor was integrated into a micro aerial vehicle (MAV) and demonstrated the capability of capturing the velocity of the MAV by sensing the relative airflow during flight.

With reduction in the scale of unmanned air vehicles, there is an increasing need for lightweight, compact, low-power sensors and alternate sensing modalities to facilitate flight control and navigation. This paper presents a novel method to fabricate a micro-scale artificial hair sensor that is capable of directional airflow sensing. The sensor consists of a high-aspect ratio hair structure attached to a thin flexible membrane. When subjected to airflow, the hair deflection induces a deformation of the membrane. Two pairs of perpendicular electrodes are attached to the membrane, which allow the sensing of airflow amplitude and direction through the measurement of differential capacitance. The sensor structure is fabricated by using two photon polymerization, which is integrated onto a miniature PCB circuit board to allow simple measurement. The sensor's responses to static displacement loading from different directions were characterized, and are in good agreement with the simulation results. Finally, the sensor's capability for directional airflow measurement was demonstrated with a clear correlation between flow speed and sensor output.

Disturbance estimation for Micro Aerial Vehicles (MAVs) is crucial for robustness and safety. In this paper, we use novel, bio-inspired airflow sensors to measure the airflow acting on a MAV, and we fuse this information in an Unscented Kalman filter (UKF) to simultaneously estimate the three-dimensional wind vector, the drag force, and other interaction forces (e.g. due to collisions, interaction with a human) acting on the robot. To this end, we present and compare a fully model-based and a deep learning-based strategy. The model-based approach considers the MAV and airflow sensor dynamics and its interaction with the wind, while the deep learning-based strategy uses a Long Short-Term Memory (LSTM) to obtain an estimate of the relative airflow, which is then fused in the proposed filter. We validate our methods in hardware experiments, showing that we can accurately estimate relative airflow of up to 4 m/s, and we can differentiate drag and interaction force.

A novel wearable device for gesture recognition was developed and tested on five subjects. The low-cost, wireless wearable device was engineered with a set of seven flexible capacitive touch electrodes sewn into an armband to be worn on the forearm between the wrist and elbow. These capacitive touch electrodes were interfaced with a microcontroller and bluetooth transceiver for measurement and transmission. As different gestures are made, flexing muscles beneath the skin affect the capacitance measured on these seven electrodes. A set of 32 gestures were tested including the 16 grasps in the Cutkosky Grasp Taxonomy and 16 basic finger and wrist motions. Several classification algorithms were tested on this data. Using a Random Forest (RF) algorithm to classify the training data, an average gesture recognition accuracy of 95.6 ± 0.06% was achieved across all five subjects individually.

This work demonstrates 3D printed soft actuators with complex shapes and remote actuation using an external magnetic field. Instead of embedding magnetic particles in a polymeric matrix, we fabricated a novel ferrofluid-based actuator, in which the fluid can be moved to different locations in the actuator to affect actuator response. We studied the effect of both the ferrofluid and the 3D printed material on the motion of simple actuators using 3D printed tubes. In addition, we 3D printed more complex actuators mimicking a human hand and a worm to demonstrate more complex motion.

This work presents the design, modeling, and fabrication of a whisker-like sensor capable of measuring the whisker's angular displacement as well as the applied moments at the base of the whisker. The sensor takes advantage of readily accessible and low-cost 3D magnetic sensors to transduce whisker deflections, and a planar serpentine spring structure at the whisker base is used to provide a mechanical suspension for the whisker to rotate. The sensor prototype was characterized, calibrated, and compared with analytical models of the spring system and the magnetic field. The prototype showed a moment sensing range of 1.1N·mm when deflected up to 19.7°. The sensitivity of the sensor was 0.38°/LSB for the angular displacement sensing, and 0.021 Nmm/LSB for the moment sensing. A fully integrated system is demonstrated to display real-time information from the whisker on a graphical interface.

Sensors to measure quadcopter ground effect are often relatively large, heavy, and require significant power, which restricts their applicability when it comes to small quadcopters and other aircraft that require lightweight and non-obstructive solutions. This paper presents the design of an elastomeric contact-resistance-based airflow sensor to measure ground effect with a mass of approximately 0.04 g and a power draw of 42 μW when in operation. It uses a rigid flap attached to the top of a flexible conductive pillar (CNT/PDMS), which deflects with varying winds speeds. A simple model is presented to describe expected trends between air flow speeds and sensor deflection and is compared with a wind tunnel characterization of the sensor for varying airflows. The sensor is characterized in a wind tunnel to identify a minimum airflow necessary for sensor functionality. Finally, sensors are attached to a Crazyflie 2.0 (Bitcraze) quadcopter and tested for performance in detecting ground effect, where there is a clear trend between sensor output and the intensity of the turbulent flow, related to proximity to ground and thrust level.

This paper describes an intuitive method for the design and fabrication of small-scale robots with multi-material compliant mechanisms in 3D. The rigid components are 3D printed, and flexures are inserted into the rigid components, creating the final mechanism. The assembled mechanisms are robust, requiring over 1 N of force to delaminate, and surviving 150,000 cycles of bending without failure. A 6 g walking quadrupedal millirobot is presented as a case study for the design and manufacturing methodology. The quadrupedal millirobot has been demonstrated moving at top speeds of 9 mm/s (0.3 body lengths/s).

BRIDGE bot is a 158 g, 10.7 × 8.9 × 6.5 cm3, magnetic-wheeled robot designed to traverse and inspect steel bridges. Utilizing custom magnetic wheels, the robot is able to securely adhere to the bridge in any orientation. The body platform features flexible, multi-material legs that enable a variety of plane transitions as well as robot shape manipulation. The robot is equipped with a Cortex-M0 processor, inertial sensors, and a modular wireless radio. A camera is included to provide images for detection and evaluation of identified problems. The robot has been demonstrated moving through plane transitions from 45° to 340° as well as over obstacles up to 9.5 mm in height. Preliminary use of sensor feedback to improve plane transitions has also been demonstrated.

Turning in small legged robots often requires extra actuators and mechanisms which consume energy and increase weight. Controllable friction on the feet of underactuated legged robots can provide extra degrees of freedom for dynamic turning. Here, we present preliminary results demonstrating that low voltage (<;200 V) electroadhesives can be adapted onto a small off-the-shelf legged robot's feet for dynamic turning. It was shown that by changing the voltage, friction can be modulated to obtain different turning radii. A turning radius of 4 cm (half the robot's body width) was achieved by applying 120 V. However, it was also shown that the current electroadhesive designs are susceptible to scratches and wrinkles that reduce their performance after multiple runs.

This work presents a method for folding 3D structures from planar microfabricated components using magnetics and an initial impulsive force. A scaling analysis demonstrates that magnetic folding can be particularly favorable at small scales and this analysis is validated through both a dynamic simulation and experimental results. Experimental results are provided by three planar-fabricated, multi-material, fold-up cubes at three different length scales (down to 1.25 mm). The three cubes folded using this method demonstrate behavior consistent with derived scaling properties, but the dynamic simulation model was deemed insufficient to capture specific details of the cubes' behavior.

This work demonstrates an all-elastomer MEMS capacitive strain sensor with high dynamic range (5000:1), and features an inexpensive molding microfabrication process. The sensor is comprised of conductive elastometric comb capacitors embedded in a dielectric. Two different sensor designs, lateral combs (LC) and transverse combs (TC), were developed to evaluate sensor sensitivity as a function of load orientation. Both sensors have combs with a gap of 30 μm, length of 4 mm, and depth of 65 μm. A linear elastic analytical model was developed to predict change in capacitance as a function of strain, and experimental results show a reasonable agreement with the theoretical predictions. The observed strain responses have high linearity and dynamic range, and negligible hysteresis. The strain resolution of the LC and TC sensors is 100 μstrain and 500 μstrain, respectively, tested up to 50% strain.

Kapton strain-based hair sensors were designed and fabricated to measure flow on a micro air vehicle. The fabrication process is carried out using a single mask and a combination of cleanroom and regular lab room processing. The processing resulted in successful realization of 6.4 mm long sensors with high yield. Associated signal conditioning circuitry was developed to extract small variations in resistance due to flow while suppressing noise. Three sensors were deployed on a fuselage shaped structure and characterized in a wind tunnel. Static linear and nonlinear estimation schemes were obtained based on the characterization data to determine the angle of attack, sideslip angle and airspeed values. For small angles of perturbation, the estimation scheme demonstrated good accuracy in determining the variables of interest. The sensors along with the signal conditioning circuitry are sufficiently lightweight that they can be used for estimating velocity states on micro air vehicles.

A paper-based electrostatic zipper actuator for printable robotics has been designed, fabricated and characterized. A simple fabrication process that utilizes paper with a carbon nanotube ink is used to create electrodes separated by either a mylar or parylene dielectric layer. A 5 cm × 1 cm actuator demonstrated a maximum static deflection of 1.8 cm and a bandwidth of approximately 12 Hz. Static power dissipation was under 1 μW. Two of these actuators are combined to demonstrate simple motion in a 6 cm × 1 cm × 1 cm robot using assymetric friction with the ground, achieving speeds up to 33 mm/min.

This work presents highly flexible elastomer and silicon micro robotic mechanisms actuated using embedded permanent magnets manipulated by an external magnetic field. The mechanisms are fabricated using a process to incorporate elastomer hinges and other features into silicon MEMS, and a method for embedding small magnets via press-fit into an elastomer sleeve. Fabricated mechanisms have demonstrated in-plane bending, out of plane bending, and underactuated compliant gripping. In-plane bending mechanisms have achieved up to 150° of deflection, out of plane bending mechanisms have achieved up to 90° bending perpendicular to the surface of the chip, and the 4.4 mm × 3.8 mm × 0.3 mm gripper can passively grip objects up to 1.5 mm in size and as small as 0.5 mm. The mechanisms demonstrated can be used as actuated portions of larger mechanisms, for out-of-plane assembly, or for on-chip manipulation.

This paper introduces a new, 50g miniature robot (Figure 1 and attached video) that uses four direct-drive hybrid wheel/legs and has been clocked at speeds exceeding 30 body lengths/s. The lowest recorded cost of transport (defined as total energy to move the robot mass a given distance) is 0.90. We discuss hardware considerations for design of robots at this scale, and the benefits of a direct-drive system over coupled transmissions. We develop a simple simulation model to examine the effects of drive speed and mechanical properties of the legs, and compare the results with experimental data on efficiency and effectiveness of locomotion with various leg designs.

Miniature legged robots have demonstrated fast locomotion at small sizes, but underactuation generally limits their performance in rapid turns and other dynamic maneuvers. In this work, the inertial effect of swinging a dynamic tail was studied as a method to achieve these rapid turns. An analytic model of a robot with a reaction wheel tail was developed to determine the effect of varying system parameters such as tail motor voltage, coefficient of friction, and tail inertia on inertial turning performance. This model was also validated experimentally using a modified off-the-shelf miniature legged robot. The same trends seen in the analytic study were also found in the experiments varying motor voltage, coefficient of friction, and tail inertia.

The TinyTeRP is a small, low-cost, modular robotics platform used to study robot sensing and control in large numbers of miniature robots. A fully assembled TinyTeRP costs approximately $50, is 1.7 × 1.8 × 2 cm3, and can move at speeds up to 50 cm/s. The robot is designed around a wheeled platform onto which different circuit boards can be stacked providing hardware modularity. The base module integrates a microcontroller with an 802.15.4 radio used for both sensing and communication between robots. An inertial sensing module used to improve single robot control is provided as an example of an additional sensing board. A simple `rendezvous' algorithm using received signal strength indicator (RSSI) data from the radio illustrates a distributed control algorithm with the TinyTeRP.

The goal of this research is to develop a lightweight, high bandwidth control actuator that can be integrated on a flapping wing nano air vehicle (NAV). Traditional control actuators for air vehicles including DC servomotors and shape memory alloy are either too heavy or too slow to control a fast moving NAV. This paper develops a new bio-inspired active tail mechanism to stabilize an inverted pendulum with the same mass and inertia as the NAV. An analysis of the dynamic model shows a critical angle at which the control actuator can no longer stabilize the pendulum varies significantly with link lengths and mass ratios. Based on this dynamic model, an LQR controller is developed and implemented as a state space controller on a microcontroller based test setup. Using a gyroscope to measure the pendulum's angular velocity and estimate the angle, the active tail mechanism was able to stabilize the pendulum for over five minutes before falling due to drift in the gyroscope sensor.

This paper describes the performance of a fluidic microrobot using Electrowetting on Dielectric (EWOD). A system to control the fluidic microrobot was designed, constructed and deployed in the NIST Mobile Microrobotics Challenge at ICRA 2011. The microrobots (0.1 M KCl and 550 μm diameter) demonstrated the ability to perform controlled maneuvers in 2-D while transporting hydrophilic objects. The EWOD system is composed of a DIP-mounted die produced via standard microfabrication techniques and containing the control electrodes / competition arena, and a transparent ITO cover slip for grounding. Key advantages of this platform include a scalable design for batch EWOD system fabrication, potential simultaneous control of multiple microrobots, and an easily portable, compact system design.

This paper describes a new process for fabricating planar, multi-material, compliant mechanisms, intended for use in small scale robotics. The process involves laser cutting the mechanism geometry from a rigid material, and refilling the joint areas with a second, elastomeric material. This method allows for a large set of potential materials, with a wide range of material properties, to be used in combination to create mechanisms with highly tailored mechanical properties. These multi-material compliant mechanisms have minimum feature sizes of approximately 100 µm and have demonstrated long lifetimes, easily surviving 100,000 bending cycles. We also present the first use of these compliant mechanisms in a 2.5cm × 2.5cm × 7.5cm, 6g hexapod. This hexapod has been demonstrated moving at speeds up to 6 cm/s, with a predicted maximum speed of up to 17 cm/s.

This paper presents the first results for jumping robots at millimeter size scales. Jumping at small sizes requires the quick release of stored energy to accelerate the robot to its takeoff velocity. Two approaches to this energy release are considered. The first is similar to the method used by most larger jumping robots and insects; energy is stored mechanically and generates thrust against the ground upon release. A new microfabrication process incorporates polymer springs for the robot leg and the resulting 4mm × 4mm × 0.3mm jumping mechanism has been launched over 32 cm into the air by hand. The second approach utilizes stored chemical energy and generates thrust by expelling gas from a chemical reaction. This energetic material has been combined with sensing, control, and power on a 4mm × 7mm × 4mm polymer chassis, and jumps in response to light stimuli have reached 8 cm in height.

This paper reports a compact, robust distance-only sensor for networked small robotic platforms. Two methods of sensing distance (neglecting heading) between robots are discussed: Received Signal Strength Indicator (RSSI) and Time Difference of Arrival (TDOA). Both implementations make use of a commercially available wireless sensor network board for communication and processing. Although RSSI requires no additional hardware, TDOA requires several additional components including a sound source and microphone. While experimental results indicate that both methods can provide distance sensing within a local neighborhood, TDOA sensing was found to be more robust and accurate, providing 1 cm distance resolution over a range of 80 cm versus 2.4 cm for RSSI. These sensors have been integrated onto mini-robotic platforms by incorporating a heading estimator and controller.

The first MEMS process integrating soft elastomers in a standard silicon-on-insulator (SOI) wafer without assembly has been demonstrated for use in microrobotic mechanisms. This process allows silicon and poly(dimethylsiloxane) (PDMS) features to be defined in-plane with feature sizes down to 2 μm. Test structures have been used to characterize the Young's modulus of the resulting PDMS at 1.4 MPa along with adhesion to silicon structures. In addition, compliant flexures have been designed, fabricated and characterized for eventual use in microrobot legs. Test structures have been mechanically folded 180° out of plane over 60 times without failure.

Photo-patternable adhesives and silicones are introduced for use in centimeter-scale robotics. Traditional approaches to making robots at this size scale require the use of expensive start-up equipment and/or precise machining, and generally yield fragile and costly robots in small numbers. The multi-material milli-robot prototyping process uses Loctite® polymer products and photolithography to rapidly fabricate robust, inexpensive, and compliant robots only centimeters in size. In this paper, the process flow is described and characterized with minimum feature sizes of 0.25 mm in polymer layers 0.18 mm thick. Both commercial and ink-jet printed masks are used for the photolithography steps. Finally, a functional inchworm robot and a small gripper have been designed and demonstrated with Nitinol shape memory alloy (SMA) used for actuation. The gripper is 1.2 g and costs $3.21 in small numbers while the inchworm robot is 7.4 g and costs $7.76 in small numbers. Building a functional robot from a computer design takes less than 1 hour.

Autonomous mobile microrobots have the potential for use in a number of applications ranging from mobile sensor networks to search and rescue. As the size of the robot gets smaller, finding an effective and efficient means of locomotion becomes especially challenging. This paper explores the limits for locomotion efficacy and efficiency by comparing simple locomotion models. Microrobot implementation issues that are not as easily modeled are also discussed. While legs and wheels may be theoretically efficient, they are not particularly effective for moving on varied surfaces and incur large efficiency penalties when implemented. Jumping may offer the best compromise for effective and efficient locomotion in millimeter-sized microrobots.

This paper presents the design and initial results for an autonomous jumping microrobot. At the millimeter size scale, jumping can offer numerous advantages for efficient locomotion, including dealing with obstacles and potentially even latching onto other larger mobile hosts. Robot design is divided into four primary areas: energy storage, actuation, power, and control. Like its biological inspiration, the flea, a jumping microrobot requires an energy storage system to store energy and release it quickly to jump. Silicone micro rubber bands have been fabricated and assembled into the microrobot for this task. To stretch these micro rubber bands, electrostatic inchworm motors are chosen as actuators due to their high forces, long throw, and low input power requirements. Finally, solar cells and a microcontroller have been chosen to power and control the microrobot. A small-scale version of this system has been prototyped with the solar cells and a simple 4-bit microcontroller driving an inchworm motor. Separately, an inchworm motor has been demonstrated pulling and storing 4.9 nJ of energy in a micro rubber band. Finally, initial tests with a probe-loaded robot prototype have demonstrated a microrobot which can potentially jump 1.2 cm straight up.

The CotsBots are inexpensive and modular mobile robots built entirely from commercial off-the-shelf components. These robots provide a convenient platform on which to investigate algorithms, cooperation, and distributed sensing in large (> 50) robot networks. Each robot is small (13 cm /spl times/ 6.5 cm base) and costs under $200. Each is equipped with on-board processing, radio communication, and a base platform for mobility. Software is written using TinyOS, an open-source, event-driven operating system for large-scale distributed sensor and actuator networks. TinyOS also provides a modular software environment where implementation details many be abstracted away from the robot application developer. A simple robot diffusion algorithm has been outlined to demonstrate the ease of using CotsBots for large-scale systems.