Smart Composite Microstructures Research Articles

Soft Polymer-Actuated Compliant Microgripper with Adaptive Vibration-Controlled Grasp and Release.

Microgrippers that incorporate soft actuators are appropriate for micromanipulation or microsurgery owing to their ability to grasp objects without causing damage. However, developing a microgripper with a large gripping range that can produce a large force with high speed remains challenging in soft actuation mechanisms. Herein, we introduce a compliant microgripper driven by a soft dielectric elastomer actuator (DEA) called a spiral flexure cone DEA (SFCDEA). The submillimeter-scale SFCDEA exhibited a controllable linear displacement over a high bandwidth and the capability of lifting 100.9 g, which was 670 times higher than its mass. Subsequently, we developed a compliant microgripper based on the SFCDEA using smart composite microstructure technology to fabricate three-dimensional gripper linkages. We demonstrated that the microgripper was able to grasp various millimeter-scale objects with different shapes, sizes, and weights without a complex feedback control owing to its compliance. We proved the versatility of our gripper in robotic manipulation by demonstrating adaptive grasping and releasing of small objects using vibrations owing to its high bandwidth.

S2worm: A Fast-Moving Untethered Insect-Scale Robot With 2-DoF Transmission Mechanism

Designing terrestrial insect-scale robot with high maneuverability and autonomy is becoming an essential challenge in the field of robotics research. Previous work has indicated that compact transmission and integrated control devices can improve the application potential. In this work, an untethered insect-scale inchworm robot is designed and fabricated by using screw theory and smart composite microstructure method, and is named S²worm. The robot weighs 4.34 g and spans 4.1 cm in length. The robot is equipped with custom designed onboard control system and high voltage boost converter to provide the driving signal for the piezoelectric bending actuator. Attributing to the novel transmission mechanism with two degrees of freedom designed based on screw theory, the S²worm can be fabricated through the smart composite microstructure method easily and shows high mobility such as high crawling speed (27.4 cm/s, 6.7 body length/s) and small turning radius (1.7 cm, 0.4 body length/s). The S²worm holds the following advantages: small size, untethered, high mobility and low energy consumption. The robot is promising for application in planetary exploration, earthquake search and constructing insect-scale multi-robot system.

A pipeline inspection robot for navigating tubular environments in the sub-centimeter scale.

In complex systems like aircraft engines and oil refinery machines, pipeline inspection is an essential task for ensuring safety. Here, we proposed a type of smart material-driven pipeline inspection robot (weight, 2.2 grams; length, 47 millimeters; diameter, <10 millimeters) that could fit into pipes with sub-centimeter diameters and different curvatures. We adopted high-power density, long-life dielectric elastomer actuators as artificial muscles and smart composite microstructure-based, high-efficiency anchoring units as transmissions. Fast assembling of components using magnets with an adjustable number of units was used to fit varying pipeline geometries. We analyzed the dynamic characteristics of the robots by considering soft material's unique properties like viscoelasticity and dynamic vibrations and tuned the activation voltage's frequency and phase accordingly. Powered by tethered cables from outside the pipe, our peristaltic pipeline robot achieved rapid motions horizontally and vertically (horizontal: 1.19 body lengths per second, vertical: 1.08 body lengths per second) in a subcentimeter-sized pipe (diameter, 9.8 millimeters). Besides, it was capable of moving in pipes with varying geometries (diameter-changing pipe, L-shaped pipe, S-shaped pipe, or spiral-shaped pipe), filled media (air or oil), and materials (glass, metal, or carbon fiber). To demonstrate its capability for pipeline inspection, we installed a miniature camera on its front and controlled the robot manually from outside. The robot successfully finished an inspection task at different speeds.

Piezoelectric actuators with on-board sensing for micro-robotic applications

We present a piezoelectric actuator design with integrated position sensing for millimeter scale mobile robotics. Actuators are fabricated using the smart composite microstructure fabrication process which consists of laser micromachining and composite lamination. Electrically isolated strain-sensing regions of the piezoelectric material undergo identical motion as the actuation layers and thus directly sense tip deflection through the piezoelectric effect. We present the design considerations of strain-sensing piezoelectric actuators which can be made over a wide range of sizes and in both unimorph and bimorph configurations. These actuators demonstrate a linear relationship between the piezo sensor voltage output and the actuator tip to tip displacement when actuated over input bias voltages ranging between 25 and 200 V and frequencies from 10 to 250 Hz. We demonstrate the applicability of strain sensing actuators for microrobotic flying robots through wing-collision and wing-degradation experiments. Actuators enabled successful detection of instantaneous wing collisions when flapping near an obstacle. Furthermore, wing degradation through loss of wing area resulted in increased wing amplitudes which were observed in the sensor. Coincident actuation and sensing within microrobots represents a meaningful step towards closed loop control capabilities of microrobots using on-board sensors.

Cockroach Milli-Robot With Improved Load Capacity

In the field of milli-robots, several methods of constructing robots by laminating materials and then folding have been developed. Among these methods, smart composite microstructures (SCM) is widely used for making lightweight small mobile robots. However, in the case of a robot manufactured by the SCM method, due to flexible and easily deformable links and joints, it is often difficult to obtain proper kinematic movement due to deformation of the structure when a heavy load is applied. In this paper, studies on the mechanism design and manufacturing were carried out to increase the load capacity of robots manufactured by SCM. First, we modified the kinematics of the robot to reduce off-axis loading on flexure joints by using a planar 6 bar leg mechanism, which was fabricated using a new multilayer SCM process. Second, the fabrication process is improved to reduce peeling of laminate structures by introducing integrated rivets at joints. Finally, alternative materials, such as balsa, are used. To verify the design and fabrication improvements, we compared the payloads after applying the proposed methods to an existing cockroach robot design. Compared to the previous design, speed with a 50-g payload increased from 7 to 30 cm per second.

Design, Prototyping and Performance Evaluation of a Bio-inspired Walking Microrobot

This paper presents the development of a small and lightweight differential hexapedal microrobot, inspired by cockroach locomotion mechanism. Detailed design, prototyping and performance evaluation are reported in this paper. The manufacturing process of the microrobot uses Smart Composite Microstructure method by employing origami-inspired techniques. Each leg of the robot has 2-DoF in Cartesian space and uses cockroach mechanism in its configuration with lightweight moving parts. This microrobot deploys an on-board power source and control system architecture which offers the advantage of self-stabilizing in a horizontal plane, head orientation control and stair climbing capability that have not previously been reported in the literature. A prototype of the microrobot has been constructed and was evaluated at different terrains.

A Novel 4-DOF Origami Grasper With an SMA-Actuation System for Minimally Invasive Surgery

Minimally invasive surgery (MIS) is one of the most challenging techniques for robot designers due to the limited size of access points, the high miniaturization level, and the dexterity needed for performing surgical tasks. Conversely, only a few microfabrication technologies are currently available for developing such small-sized systems, which allow safe operations in human bodies. In order to match these challenges in MIS, both design and integration of actuation systems should proceed in parallel with an identification of most effective transmission mechanisms and kinematics. In this paper, an origami parallel module that generates two rotations and one translation is integrated with a twisting module and a compliant gripper to form a novel four-degree-of-freedom grasper. The rotational motion leads to the pitch and yaw motion of the gripper, while the translational motion is converted to a roll motion of the gripper via the twisting module that is stacked on top of the parallel module. In light of plane-symmetric properties of the origami structure in the parallel module, both inverse and forward kinematics are resolved with a geometric approach, revealing a unique joint space and a kinematic mapping of the parallel module, leading to the design of two sets of on-board actuation systems. During the analysis, bending motion of a central spring and static properties of the compliant gripper are modeled using finite-element methods. The structure of the twisting module for motion transmission of the grasper is designed and fabricated using origami folding techniques. Gripping forces of the compliant gripper are evaluated in experimental tests. Further analyses of the system performance are addressed in accordance with the scaling ratio of miniaturization and the scalability of the system is demonstrated by a millimeter-sized origami parallel module produced by the smart composite microstructure fabrication process.

Integrated Manufacture of Exoskeletons and Sensing Structures for Folded Millirobots

Inspired by the exoskeletons of insects, we have developed a number of manufacturing methods for the fabrication of structures for attachment, protection, and sensing. This manufacturing paradigm is based on infrared laser machining of lamina and the bonding of layered structures. The structures have been integrated with an inexpensive palm-sized legged robot, the VelociRoACH [Haldane et al., 2013, “Animal-Inspired Design and Aerodynamic Stabilization of a Hexapedal Millirobot,” IEEE/RSJ International Conference on Robotics and Automation, Karlsruhe, Germany, May 6–10, pp. 3279–3286]. We also present a methodology to design and fabricate folded robotic mechanisms, and have released an open-source robot, the OpenRoACH, as an example implementation of these techniques. We present new composite materials which enable the fabrication of stronger, larger scale smart composite microstructures (SCM) robots. We demonstrate how thermoforming can be used to manufacture protective structures resistant to water and capable of withstanding terminal velocity falls. A simple way to manufacture traction enhancing claws is demonstrated. An electronics layer can be incorporated into the robot structure, enabling the integration of distributed sensing. We present fabrication methods for binary and analog force sensing arrays, as well as a carbon nanotube (CNT) based strain sensor which can be fabricated in place. The presented manufacturing methods take advantage of low-cost, high accuracy two-dimensional fabrication processes which will enable low-cost mass production of robots integrated with mechanical linkages, an exoskeleton, and body and limb sensing.

Flea-Inspired Catapult Mechanism for Miniature Jumping Robots

Fleas can jump more than 200 times their body length. They do so by employing a unique catapult mechanism: storing a large amount of elastic energy and releasing it quickly by torque reversal triggering. This paper presents a flea-inspired catapult mechanism for miniature jumping robots. A robotic design was created to realize the mechanism for the biological catapult with shape memory alloy (SMA) spring actuators and a smart composite microstructure. SMA spring actuators replace conventional actuators, transmissions, and the elastic element to reduce the size. The body uses a four-bar mechanism that simulates a flea's leg kinematics with reduced degrees of freedom. Dynamic modeling was derived, and theoretical jumping was simulated to optimize the leg design for increased takeoff speed. A robotic prototype was fabricated with 1.1-g weight and 2-cm body size that can jump a distance of up to 30 times its body size.

Design and manufacturing of a controllable miniature flapping wing robotic platform

In this work we present the design of a scalable, controllable, miniature flapping wing robot. The design effort comprises considerations of the number of driving actuators for controllability, body structure for both weight minimization and rigidity, and overall compactness of the robot design. This results in the development of the spherical four-bar transmission mechanism, with a single-wing prototype experimentally characterized. A dual-wing robot design manufactured via the smart composite microstructures technique is presented, featuring independent wing actuation. Finite-element analysis of the final airframe design is presented, ensuring vibration modes out of the operation range of the platform and high rigidity. A working prototype is manufactured and experiments are conducted characterizing the robot’s lift production capabilities and ensuring minimal wing coupling. A scaling law of the proposed design is presented based on momentum theory, predicting an increase of the lift/weight ratio with decreasing size. An optimization methodology for the parameters of a scaled down prototype is presented, based on a developed theoretical simulation and design tool. Finally, a 1/2 scaled down prototype using the optimized parameters is built and tested, featuring a lift/weight ratio of 3/8.

Myriapod-like ambulation of a segmented microrobot

Segmented myriapod-like bodies may offer performance benefits over more common fixed body morphologies for ambulation. Here, the design of a segmented ambulatory microrobot with a flexible backbone is presented. A dynamic model describing the motion of the microrobot is used to determine body parameters. A three-segment microrobot was fabricated using the Smart Composite Microstructures process and piezoelectric bimorph actuators, and forward locomotion on a flat surface was demonstrated. The footprint of the 750 mg microrobot is 3.5 by 3.5 cm, and it has potential advantages over rigid body hexapedal microrobots in climbing, versatility, and stability.

Review of manufacturing processes for soft biomimetic robots

This paper reviews various processes for manufacturing new type of robots termed “soft biomimetic robots.” Most robots are made of rigid metallic materials. But in recent years, various biomimetic robots based on soft materials and compliant parts have been developed. New manufacturing processes are required to fabricate these types of robots, and the processes include Shape Deposition Manufacturing (SDM) and Smart Composite Microstructures (SCM). Since the design of robots are limited by the available material and manufacturing processes, it is important to develop new manufacturing processes that will enable development of novel soft biomimetic robots. In this paper, various manufacturing processes which can be applied to soft robot fabrication are summarized, and features of those processes are described. Processes are divided into three categories; soft robot body fabrication, actuators for soft robots and stretchable electronics. This review provides a guideline for selecting manufacturing processes for soft robots and developing new processes that will enable new type of robots to be designed.

Microrobot Design Using Fiber Reinforced Composites

Mobile microrobots with characteristic dimensions on the order of 1cm are difficult to design using either microelectromechanical systems technology or precision machining. This is due to the challenges associated with constructing the high strength links and high-speed, low-loss joints with micron scale features required for such systems. Here, we present an entirely new framework for creating microrobots, which makes novel use of composite materials. This framework includes a new fabrication process termed smart composite microstructures (SCM) for integrating rigid links and large angle flexure joints through a laser micromachining and lamination process. We also present solutions to actuation and integrated wiring issues at this scale using SCM. Along with simple design rules that are customized for this process, our new complete microrobotic framework is a cheaper, quicker, and altogether superior method for creating microrobots that we hope will become the paradigm for robots at this scale.