Providing oral capsule robots with additional degrees of freedom (DOF), such as robotic arms, is crucial for enhancing their functionality within the body. However, a key challenge arises when using rotating magnetic fields to drive the motor within the robot, as the resulting torque causes the entire capsule to rotate. In this work, we propose a novel approach to actuate a 2 DOF parallel link robot arm integrated into a capsule robot, using external magnetic fields. Our method employs two identical magnetic motors we proposed in a previous study, each driven by an oscillating magnetic field, which alternates direction along a specific axis. By independently controlling the rotation of each motor through the same magnetic field, ensemble control is achieved. The symmetrically arranged motors exhibit different angular velocities, enabling dexterous movement of the robot arm. We further theoretically show that this approach significantly reduces the torque exerted on the robot compared to traditional approaches using rotating magnetic fields. Finally, we demonstrate the performance of the robot by moving its arms and the attached end-effector along a pre-defined trajectory.

While many inkjet printers employ only four types of ink (i.e. CKMY) to produce a wide range of colors, numerous technical challenges still exist for contemporary 3D printers to fabricate various materials and generate composite products such as electric devices. Conversely, there have been attempts and endeavors to make things through self-assembly of parts, analogous to the autonomous and decentralized development process of the human body from just 20 types of amino acids. In our previous work, we proposed a method for the rapid production of 3D objects using the centimeter-sized modules (referred to as Roblets) capable of generating a 2D structure and subsequently self-folding themselves into a 3D configuration, akin to origami. To further leverage the capability of generating a wide variety of different types of structures by combining different modules, this research studies a method of automatically selecting and supplying modules using environmental cues. More precisely, we developed a mechanism to couple different modules corresponding to three different environments (on a flat surface, on low-dense saline, and on saturated saline) and yielded different module configurations. The process of self-assembly necessitated the application of perturbation, which was realized by imparting magnetic torque originating from an external magnetic field onto the magnets embedded in the modules.

This paper addresses the challenge of actuating millimetre-sized motors, which are wirelessly driven by external magnetic fields. Traditional approaches, relying on rotating magnetic fields, often inadvertently cause the entire robot – especially if it is small and lightweight – to rotate, instead of a specified shaft in the motor. To overcome this issue, our study introduces a novel mechanism that leverages symmetrically configured magnetic motors to cancel out the torques, thus preventing unwanted rotation of the robot. This is achieved by utilizing a magnetic field along a single axis to induce rotational movement. The design features two millimetre-sized rotating magnets that interact to achieve a 90◦rotation, complemented by an external magnetic field that accomplishes the remaining 270◦, thus completing a full rotation. Furthermore, we demonstrate that applying a perpendicularly oriented magnetic field can inversely affect the motor’s rotation direction. A proof-of-concept experiment employing this mechanism successfully actuated a gripper in a water tank while it is free-floating, showcasing its potential for enhancing robotic applications at the sub-centimeter scale, where the small net torque of a miniature motor is essential.

Inspired by human proteins that are synthesized from only 20 types of amino acids, the development of self-assembly methods that allow robots to be built simply by randomly stirring the parts has been explored for many years. The key challenges include how to synthesize parts in pieces into a three-dimensional functional structure in a practical time, and subsequently, achieve a controlled robotic motion, all with minimal human intervention. This study proposes a method of self-assembling a 3D robot by first self-assembling random parts into a 2D structure and then self-folding it into a 3D shape. Once self-folded, the robot, whose compositional parts contain magnets, becomes capable of performing basic tasks such as block-pushing upon an application of an external magnetic field. Self-assembly from parts into a two-dimensional structure was performed by repeatedly colliding the parts with each other, and combining them with complementary-shaped parts, like matching jigsaw puzzle pieces. Self-folding was performed by shrinking a heat-responsive film attached across the hinge of each assembly part in hot water, causing the entire 2D structure to self-fold. The experiment demonstrated a series of 13 parts self-assembling into the shape of a 3D beetle, then walking and pushing an object in 13 minutes. The self-assembly process is programmed (mechanically) to generate the same geometry even if the number of parts is greater than the necessary number for the structure, thus is capable of generating multiple structures simultaneously.

In biomedical engineering, robotic implants provide new methods to restore and improve bodily function, and regenerate tissue. A significant challenge with the design of these devices is to safely actuate them for weeks or months, while they are residing in a patient's body. Magnetic, and other force-at-distance actuation methods, allow mechanisms to be controlled remotely and without contact or line of sight to the device. In this paper, we present a novel magnetic field driven wireless motor. The motor drives a robotic implant for the treatment of long gap esophageal atresia and short bowel syndrome. The motor is equipped with two oppositely oriented permanent magnets which experience forces in opposite directions when a magnetic field is applied tangential to the magnets' directions. The implant can produce a force of 2 N. It is demonstrated with an ex vivo porcine esophagus.

Inspired by the traditional art of paper folding, origami, autonomous production of 3D structures from 2D sheets can be achieved by the implementation of self-folding techniques. One technique to achieve such transformation is the usage of thermo-responsive smart materials such as self-folding polymeric films, which can be controlled by heat to shrink. Achieving remote self-folding with a practical approach remains a major challenge due to the requirement for specific environments, or having to accompany electronics on origami, which limits the complexity of the origami design. In this paper, we present a wireless method to trigger the thermo-responsive self-folding process of the origami robots through magnetic induction. The proposed method is applicable for all electrically conductive materials and can wirelessly fold a mobile origami robot with a size of 32 × 30 mm2. This method eliminates the need for inclusion of electronics on the origami or usage of complicated trigger methods and environmental conditions, allowing the robot to fold in a wider range of applications such as in constrained spaces.

A button battery accidentally ingested by a toddler or small child can cause severe damage to the stomach within a short period of time. Once a battery lands on the surface of the esophagus or stomach, it can run a current in the tissue and induce a chemical reaction resulting in injury. Following our previous work where we presented an ingestible magnetic robot for button battery retrieval, this study presents a remotely achieved novel localization method of a button battery with commonly available magnetic sensors (Hall-effect sensors). By applying a direct magnetic field to the button battery using an electromagnetic coil, the battery is magnetized, and hence it becomes able to be sensed by Hall-effect sensors. Using a trilateration method, we were able to detect the locations of an LR44 button battery and other ferromagnetic materials at variable distances. Additional four electromagnetic coils were used to autonomously navigate a magnet-containing capsule to dislocate the battery from the affected site.

Soft robotics has advanced the field of biomedical engineering by creating safer technologies for interfacing with the human body. One of the challenges in this field is the realization of modular soft basic constituents and accessible assembly methods to increase the versatility of soft robots. We present a soft pneumatic actuator composed of two elastomeric strands that provide interdependent axial and radial expansion due to the modularity of the components and their helical arrangement. The actuator reaches 35% of elongation with respect to its initial height and both chambers achieve forces of 1N at about 19kPa. We describe the design, fabrication, modeling and benchtop testing of the soft actuator towards realizing 3D functional structures with potential medical applications. An example of application for soft medical robots is tissue regenerative for the long-gap esophageal atresia condition.

Gastric ulcer is a chronic and complex (and often complete) erosion of the stomach wall that happens as a complication of a previous chronic, inflammatory process. It represents a catastrophic situation in which the patient is critical and its conditions need to be treated fast. This study presents a remotely navigatable and deployable ingestible patch and plug for gastric ulcer treatment. The patch/plug structure is made of agarose hydrogel that can change rigidity through hydration and dehydration. When dehydrated, it is rigid and can maintain a folded configuration so it can be ingested as a “pill”. This can be guided to the targeted location by a magnetic field, and be deployed instantly by hydration, namely by supplying water from the mouth. Due to the deployable origami design, it exhibits an expansion of 10 times its initial surface area, making the device suitable for the use of dressing a surface as a patch, and filling a hole as a plug.

This paper presents an end-to-end approach to automate the design and fabrication process for self-folding origami structures. Self-folding origami structures are robotic sheets composed of rigid tiles and joint actuators. When they are exposed to heat, each joint folds into a preprogrammed angle. Those folding motions transform themselves into a structure, which can be used as body of 3-D origami robots, including walkers, analog circuits, rotational actuators, and microcell grippers. Given a 3-D model, the design algorithm automatically generates a layout printing design of the sheet form of the structure. The geometric information, such as the fold angles and the folding sequences, is embedded in the sheet design. When the sheet is printed and baked in an oven, the sheet self-folds into the given 3-D model. We discuss, first, the design algorithm generating multiple-step self-folding sheet designs, second, verification of the algorithm running in O(n2) time, where n is the number of the vertices, third, implementation of the algorithm, and finally, experimental results, several self-folded 3-D structures with up to 55 faces and two sequential folding steps.

This paper describes additive self-folding, an origami-inspired rapid fabrication approach for creating actuatable compliant structures. Recent work in 3-D printing and other rapid fabrication processes have mostly focused on rigid objects or objects that can achieve small deformations. In contrast, soft robots often require elastic materials and large amounts of movement. Additive self-folding is a process that involves cutting slices of a 3-D object in a long strip and then pleat folding them into a likeness of the original model. The zigzag pattern for folding enables large bending movements that can be actuated and controlled. Gaps between slices in the folded model can be designed to provide larger deformations or higher shape accuracy. We advance existing planar fabrication and self-folding techniques to automate the fabrication process, enabling highly compliant structures with complex 3-D geometries to be designed and fabricated within a few hours. We describe this process in this paper and provide algorithms for converting 3-D meshes into additive self-folding designs. The designs can be rapidly instrumented for global control using magnetic fields or tendon-driven for local bending. We also describe how the resulting structures can be modeled and their responses to tendon-driven control predicted. We test our design and fabrication methods on three models (a bunny, a tuna fish, and a starfish) and demonstrate the method's potential for actuation by actuating the tuna fish and starfish models using tendons and magnetic control.

We present a new teleoperated micromanipulation system in which all units of the system, wearable user interface devices and a slave micromanipulator, are manufactured by engraving, cutting, and folding two-dimensional materials. The designed manipulation system employs a simple hydraulic mechanism consisting of pairs of syringes that have different diameters, which allows for motion reduction and physical interaction between the master and the slave. As a result, users can precisely manipulate micro-objects without tremor, which was previously difficult with bare hands. This paper presents design considerations and features fabrication methods, performance metrics of this creative manipulation system, and a range of high-level micromanipulation abilities such as pick-and-place, microseparation, and three-dimensional microassembly. Highlighting rapid design and fabrication of a low-cost precision micromanipulation system, this paper proposes new applications of folded machines to wearable robots and microrobotics.

Developing miniature robots that can carry out versatile clinical procedures inside the body under the remote instructions of medical professionals has been a long time challenge. In this paper, we present origami-based robots that can be ingested into the stomach, locomote to a desired location, patch a wound, remove a foreign body, deliver drugs, and biodegrade. We designed and fabricated composite material sheets for a biocompatible and biodegradable robot that can be encapsulated in ice for delivery through the esophagus, embed a drug layer that is passively released to a wounded area, and be remotely controlled to carry out underwater maneuvers specific to the tasks using magnetic fields. The performances of the robots are demonstrated in a simulated physical environment consisting of an esophagus and stomach with properties similar to the biological organs.

A miniature robotic device that can fold-up on the spot, accomplish tasks, and disappear by degradation into the environment promises a range of medical applications but has so far been a challenge in engineering. This work presents a sheet that can self-fold into a functional 3D robot, actuate immediately for untethered walking and swimming, and subsequently dissolve in liquid. The developed sheet weighs 0.31 g, spans 1.7 cm square in size, features a cubic neodymium magnet, and can be thermally activated to self-fold. Since the robot has asymmetric body balance along the sagittal axis, the robot can walk at a speed of 3.8 body-length/s being remotely controlled by an alternating external magnetic field. We further show that the robot is capable of conducting basic tasks and behaviors, including swimming, delivering/carrying blocks, climbing a slope, and digging. The developed models include an acetone-degradable version, which allows the entire robot's body to vanish in a liquid. We thus experimentally demonstrate the complete life cycle of our robot: self-folding, actuation, and degrading.

Computational thinking is an important part of a modern education, and robotics provides a powerful tool for teaching programming logic in an interactive and engaging way. The robot garden presented in this paper is a distributed multi-robot system capable of running autonomously or under user control from a simple graphical interface. Over 100 origami flowers are actuated with LEDs and printed pouch motors, and are deployed in a modular array around additional swimming and crawling folded robots. The garden integrates state-of-the-art rapid design and fabrication technologies with distributed systems software techniques to create a scalable swarm in which robots can be controlled individually or as a group. The garden can be used to teach basic algorithmic concepts through its distributed algorithm demonstration capabilities and can teach programming concepts through its education-oriented user interface.

This study demonstrates a new approach to autonomous folding for the body of a 3D robot from a 2D sheet, using heat. We approach this challenge by folding a 0.27-mm sheetlike material into a structure. We utilize the thermal deformation of a contractive sheet sandwiched by rigid structural layers. During this baking process, the heat applied on the entire sheet induces contraction of the contracting layer and thus forms an instructed bend in the sheet. To attain the targeted folding angles, the V-fold spans method is used. The targeted angle θout can be kinematically encoded into crease geometry. The realization of this angle in the folded structure can be approximately controlled by a contraction angle θin. The process is non-reversible, is reliable, and is relatively fast. Our method can be applied simultaneously to all the folds in multi-crease origami structures. We demonstrate the use of this method to create a lightweight mobile robot.

This paper presents an end-to-end approach for creating 3D shapes by self-folding planar sheets activated by uniform heating. These shapes can be used as the mechanical bodies of robots. The input to this process is a 3D geometry (e.g. an OBJ file). The output is a physical object with the specified geometry. We describe an algorithm pipeline that (1) identifies the overall geometry of the input, (2) computes a crease pattern that causes the sheet to self-fold into the desired 3D geometry when activated by uniform heating, (3) automatically generates the design of a 2D sheet with the desired pattern and (4) automatically generates the design files required to fabricate the 2D structure. We demonstrate these algorithms by applying them to complex 3D shapes. We demonstrate the fabrication of a self-folding object with over 50 faces from automatically generated design files.

This paper presents a methodology and validation of print-and-self-fold electric devices. For printing functional structures for robotic use, we realize electric circuitry based on metallic polyester film (MPF). By exploiting the unique material properties of MPF, we developed fundamental electric devices, namely a resistor, capacitor, and inductor. The developed polyvinyl chloride laminated MPF sheet shows reliable self-folding processes under a heat application, and it configures 3D electric devices. Due to the pre-resolved kinematic design, these devices feature elasticity, making them suitable as sensors and actuators in soft circuits. Here we testify to a self-assembled variable resistor and capacitive strain sensor. An actuation mechanism consisting of a folded contractible coil is also considered and shown. Finally, an RLC circuit obtained from the integration of all the developed devices is demonstrated, in which the coil based actuator is controlled by reading a variable capacitive strain sensor.

In this study, we demonstrate a new approach to autonomous folding for the body of a 3D robot from a 2D sheet using heat. We approach this challenge by folding a 0.27 mm sheet-like material into a structure. We utilize the thermal deformation of a contractive sheet sandwiched by rigid structural layers. During this “baking” process, the heat applied on the entire sheet induces contraction of the contracting layer and, thus, forms an instructed bend in the sheet. To attain the targeted folding angles, the V-fold Spans method is used. The targeted angle θoutcan be kinematically encoded into crease geometry. The realization of this angle in the folded structure can be approximately controlled by a contraction angle θin. The process is non-reversible, is reliable, and it is relatively fast. Our method can be applied simultaneously to all the folds in multi-creased origami structures. We demonstrate the use of this method to create a light-weight mobile robot.

Nature regularly uses self-folding as an efficient approach to automated fabrication. In engineered systems, however, the use of self-folding has been primarily restricted to the assembly of small structures using exotic materials and/or complex infrastructures. In this paper we present three approaches to the self-folding of structures using low-cost, rapid-prototyped shape memory laminates. These structures require minimal deployment infrastructure, and are activated by light, heat, or electricity. We compare the fabrication of a fundamental structure (a cube) using each approach, and test ways to control fold angles in each case. Finally, for each self-folding approach we present a unique structure that the approach is particularly suited to fold, and discuss the advantages and disadvantages of each approach.

Self-organization is a phenomenon found in biomolecular self-assembly by which proteins are spontaneously driven to assemble and attain various functionalities. This study reports on self-organized behavior in which distributed centimeter-sized modules stochastically aggregate and exhibit a translational wheeling motion. The system consists of two types of centimeter-sized water-floating modules: a triangular-shaped module that is equipped with a vibration motor and a permanent magnet (termed the active module), which can quasi-randomly rove around; and circular modules that are equipped with permanent magnets (termed passive modules). In its quasi-random movement in water, the active module picks up passive modules through magnetic attraction. The contacts between the modules induce a torque transfer from the active module to the passive modules. This results in rotational motion of the passive modules. As a consequence of the shape difference between the triangular module and the circular module, the passive modules rotate like wheels, being kept on the same edges as the active module. The motion of the active module is examined, as well as the characteristics and behavior of the self-organization process.

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 investigate possible means of communication between plants and machines. Plants are capable of sensing a variety of environmental information. In particular, Avocado trees have an apparent response to increasing drought levels. We read out two different communication channels: morphological changes (leaf inclination) and the electric potential of the stem (biopotential) using distance sensors and biopotential electrodes, respectively. Leaf inclination reliably triggers irrigation, whereas the changes of the biopotential indicate water uptake and can be used to automatically stop the irrigation. Hence, through systematic experiments we demonstrate that morphological changes and biopotentials provide suitable control signals for interfacing plants with machines, and open a possibility to exploit abilities of plants in robotic systems.

Self-assembly is a process in which individual components form an organized structure as a consequence of local interactions. When using magnetics to create interaction forces, the magnetic flux distribution of a self-assembling system changes as its assembly state varies. Since Hall effect sensors are a convenient and effective means to detect changes in the magnetic field, we explore their applicability to monitoring the morphology of such magnetically self-assembling systems. We find that optimal positions for the sensor can be found where the flux changes maximally. Our analysis is applied to two different systems by deriving the flux changes for all possible states, and theoretical flux changes are verified with experiments. In addition, we show that a small number of sensors is sufficient for robust state determination. In addition to state detection, experiments show the potential for angle measurement for compliant cylindrical magnet joints using a single Hall sensor.

Self-assembly is a process through which an organized structure can spontaneously form from simple parts. Taking inspiration from biological examples of self-assembly, we designed and built a water-based modular robotic system consisting of autonomous plastic tiles capable of aggregation on the surface of water. In this paper, we investigate the effect of the morphology (here: shape) of the tiles on the yield of the self-assembly process, that is, on the final amount of the desired aggregate. We describe experiments done with the real system as well as with a computer simulation thereof. We also present results of a mathematical analysis of the modular system based on chemical rate equations which point to a power-law relationship between yield rate and shape. Using the real system, we further demonstrate how through a single parameter (here: the externally applied electric potential) it is possible to control the self-assembly of propeller-like aggregates. Our results seem to provide a starting point (a) for quantifying the effect of morphology on the yield rates of self-assembly processes and (b) for assessing the level of modular autonomy and computational resources required for emergent functionality to arise.

We present a novel type of inter-module connection mechanism for waterborne modular robotic systems. The proposed mechanism exploits the thermoelectric effect to cool down and freeze the water between two modules thus causes them to attach to each other. We validate the feasibility of this mechanism by embedding a Peltier heat pump (m = 0.8 g) in two types of cm scale self-assembly systems, one in which the modules are free to move and one in which the modules are linked together by hinges. Our experimental results demonstrate that the proposed Peltier-based connector has (a) a high bond strength/weight ratio for a rather large range of temperatures and (b) is rather robust against misalignments between docking modules, making it a useful alternative to current connection mechanisms for small scale low autonomy self-assembly systems.

We present a novel type of inter-module connection mechanism for waterborne modular robotic systems. The proposed mechanism exploits the thermoelectric effect to cool down and freeze the water between two modules thus causes them to attach to each other. We validate the feasibility of this mechanism by embedding Peltier heat pumps (m = 0.8 g) in a cm scale self-assembly system. Our experimental results demonstrate that the proposed Peltier-based connector has (a) a high bond strength/weight ratio for a rather large range of temperatures and (b) is rather robust against misalignments between docking modules, making it a useful alternative to current connection mechanisms for small scale low autonomy self-assembly systems.

In this paper we show how geometric constraints enable developmental processes to generate the morphology of three-dimensional folding sheets more easily. These sheets consist of artificial cells, which are connected and are able to exert forces on each other. To keep track of the complex pattern of connectivity, we introduce a cell connection map, which represents the internal states of the cells and is used to visualize these states. The performed simulations show that the system can easily produce some complicated morphogenetic forms and we show that the forms can be quantified as entropy by evaluating the cell connection map. This entropy was also used as a fitness function in order to evolve shapes. We would like to point out that once an adequate geometric constraint is given, the forms are generated by simple internal states and cell-cell interactions.