Microrobotics: A Commemorative Issue in Honor of Professor Robert J. Wood

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E:Engineering and Technology".

Deadline for manuscript submissions: closed (10 July 2022) | Viewed by 20362

Special Issue Editors


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Guest Editor
Department of Biomedical Engineering, City University of Hong Kong, Hong Kong SAR, China
Interests: bio-inspired robots; micro aerial vehicles; control and dynamics

E-Mail Website
Guest Editor
Soft and Micro Robotics Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Interests: microrobotics; soft robotics; insect flight; aerodynamics

Special Issue Information

Dear Colleagues, 

Robert J. Wood is the Charles River Professor of Engineering and Applied Sciences in the Harvard John A. Paulson School of Engineering and Applied Sciences, an Associate Faculty member of the Wyss Institute for Biologically Inspired Engineering, and a National Geographic Explorer. Prof. Wood completed his M.S. and Ph.D. degrees in the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley. He is founder of the Harvard Microrobotics Lab, which leverages expertise in microfabrication for the development of biologically inspired robots with feature sizes on the micrometer to centimeter scale. He is the winner of multiple awards for his work including the DARPA Young Faculty Award, NSF Career Award, ONR Young Investigator Award, Air Force Young Investigator Award, Technology Review’s TR35, and multiple best paper awards. In 2010, Wood received the Presidential Early Career Award for Scientists and Engineers from President Obama for his work in microrobotics. In 2012, he was selected for the Alan T. Waterman award, the National Science Foundation’s most prestigious early career award. In 2014, he was named one of National Geographic’s “Emerging Explorers”. Wood’s group is also dedicated to STEM education by using novel robots to motivate young students to pursue careers in science and engineering. 

Microrobotics is an interdisciplinary field that integrates tools from robotics, physics, material sciences, and microfabrication to develop robotic systems at the micro and nano scales. This Special Issue honors Professor Robert J. Wood for his contribution to the development of bio-inspired meso-scale fabrication and actuation technology. Most notably, Prof. Wood’s team has developed a highly agile insect-scale aerial robot known as the RoboBee, which is one of the lightest and smallest aerial robots that can demonstrate remarkable flight maneuvers. Prof. Wood’s work has led to novel design methodology, microfabrication techniques, microscale sensors and actuators, power electronics, and dynamics and control methods for microscale systems. 

Recent advances in microrobotic research has led to versatile, robust, and agile microscale robots that can move in multiple environments, perform complex tasks, and demonstrate functions that are unseen in traditional robots. At the millimeter scale, diminishing inertial forces and growing surface effects pose unique challenges and opportunities for microscale systems. To optimize power density at the millimeter or micrometer scale, novel electrostatic, piezoelectric, and magnetic actuators replace traditional electromagnetic motors in many microscale mobile robots. To demonstrate new capabilities such as perching and locomotion on the water surface, microscale system leverage surface effects that are often insignificant in large scale systems. Meanwhile, microscale robotic systems face unique challenges in design, fabrication, actuation, sensing, control, and power. To enable future microrobotic applications, we still require innovations in many areas such as developing power-dense actuators, compact and efficient power electronics, new energy sources, scalable microfabrication techniques, and control autonomy. This Special Issue aims to identify and address major challenges in frontier microrobotic research. The topics of interest include but are not limited to:

  • Novel microscale (<1g) active materials, sensors, and actuators;
  • Mechanism design and microfabrication techniques;
  • Multifunctional or swarm magnetic microrobots;
  • Microrobots in medical applications;
  • Kinematics, dynamics, and control of micro and millirobot;
  • Applications of surface phenomena (surface tension, electrostatics) in microscale systems;
  • Mobile (aerial, terrestrial, or aquatic) microrobotic systems;
  • Power electronics and power sources for microscale robots.

Dr. Pakpong Chirarattananon
Dr. Yufeng (Kevin) Chen
Guest Editors

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Keywords

  • Microscale bio-inspired robotics
  • Microfabrication
  • Microscale mechanics
  • Soft and active materials
  • Actuators and sensors
  • Dynamics and control

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Published Papers (6 papers)

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Research

14 pages, 3657 KiB  
Article
An Insect-Inspired Terrains-Adaptive Soft Millirobot with Multimodal Locomotion and Transportation Capability
by Han Huang, Yu Feng, Xiong Yang, Liu Yang and Yajing Shen
Micromachines 2022, 13(10), 1578; https://doi.org/10.3390/mi13101578 - 22 Sep 2022
Cited by 7 | Viewed by 2591
Abstract
Inspired by the efficient locomotion of insects in nature, researchers have been developing a diverse range of soft robots with simulated locomotion. These robots can perform various tasks, such as carrying medicines and collecting information, according to their movements. Compared to traditional rigid [...] Read more.
Inspired by the efficient locomotion of insects in nature, researchers have been developing a diverse range of soft robots with simulated locomotion. These robots can perform various tasks, such as carrying medicines and collecting information, according to their movements. Compared to traditional rigid robots, flexible robots are more adaptable and terrain-immune and can even interact safely with people. Despite the development of biomimetic principles for soft robots, how their shapes, morphology, and actuation systems respond to the surrounding environments and stimuli still need to be improved. Here, we demonstrate an insect-scale soft robot with multi-locomotion modes made by Ecoflex and magnetic particles, which can be actuated by a magnetic field. Our robot can realize four distinct gaits: horizontal tumbling for distance, vertical tumbling for height, imitation of gastropod writhing, and inchworm-inspired crawling for cargo delivery. The soft compliant structure and four locomotion modes make the robot ideal for maneuvering in congested or complex spaces. In addition to linear motion (~20 mm/s) and turning (50°/s) on a flat terrain, the robot can also maneuver on various surface conditions (such as gaps, smooth slopes, sand, muddy terrain, and water). These merits, together with the robot’s high load-carrying capacity (5 times its weight), low cost, obstacle-crossing capability (as high as ~50% its length), and pressure resistance (70 kg), allow for a wide variety of applications. Full article
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16 pages, 54271 KiB  
Article
Soft Molds with Micro-Machined Internal Skeletons Improve Robustness of Flapping-Wing Robots
by Hang Gao, James Lynch and Nick Gravish
Micromachines 2022, 13(9), 1489; https://doi.org/10.3390/mi13091489 - 7 Sep 2022
Cited by 1 | Viewed by 2355
Abstract
Mobile millimeter and centimeter scale robots often use smart composite manufacturing (SCM) for the construction of body components and mechanisms. The fabrication of SCM mechanisms requires laser machining and laminating flexible, adhesive, and structural materials into small-scale hinges, transmissions, and, ultimately, wings or [...] Read more.
Mobile millimeter and centimeter scale robots often use smart composite manufacturing (SCM) for the construction of body components and mechanisms. The fabrication of SCM mechanisms requires laser machining and laminating flexible, adhesive, and structural materials into small-scale hinges, transmissions, and, ultimately, wings or legs. However, a fundamental limitation of SCM components is the plastic deformation and failure of flexures. In this work, we demonstrate that encasing SCM components in a soft silicone mold dramatically improves the durability of SCM flexure hinges and provides robustness to SCM components. We demonstrate this advance in the design of a flapping-wing robot that uses an underactuated compliant transmission fabricated with an inner SCM skeleton and exterior silicone mold. The transmission design is optimized to achieve desired wingstroke requirements and to allow for independent motion of each wing. We validate these design choices in bench-top tests, measuring transmission compliance, kinematics, and fatigue. We integrate the transmission with laminate wings and two types of actuation, demonstrating elastic energy exchange and limited lift-off capabilities. Lastly, we tested collision mitigation through flapping-wing experiments that obstructed the motion of a wing. These experiments demonstrate that an underactuated compliant transmission can provide resilience and robustness to flapping-wing robots. Full article
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16 pages, 5904 KiB  
Article
A Miniature Soft Sensor with Origami-Inspired Self-Folding Parallel Mechanism
by Yongqi Shi, Gang Wang, Wenguang Sun, Yunfeng Ya, Shuhan Liu, Jiongjie Fang, Feiyang Yuan, Youning Duo and Li Wen
Micromachines 2022, 13(8), 1188; https://doi.org/10.3390/mi13081188 - 28 Jul 2022
Cited by 6 | Viewed by 3042
Abstract
Miniature soft sensors are crucial for the perception of soft robots. Although centimeter-scale sensors have been well developed, very few works addressed millimeter-scale, three-dimensional-shaped soft sensors capable of measuring multi-axis forces. In this work, we developed a millimeter-scale (overall size of 6 mm [...] Read more.
Miniature soft sensors are crucial for the perception of soft robots. Although centimeter-scale sensors have been well developed, very few works addressed millimeter-scale, three-dimensional-shaped soft sensors capable of measuring multi-axis forces. In this work, we developed a millimeter-scale (overall size of 6 mm × 11 mm × 11 mm) soft sensor based on liquid metal printing technology and self-folding origami parallel mechanism. The origami design of the sensor enables the soft sensor to be manufactured within the plane and then fold into a three-dimensional shape. Furthermore, the parallel mechanism allows the sensor to rotate along two orthogonal axes. We showed that the soft sensor can be self-folded (took 17 s) using a shape-memory polymer and magnets. The results also showed that the sensor prototype can reach a deformation of up to 20 mm at the tip. The sensor can realize a measurement of external loads in six directions. We also showed that the soft sensor enables underwater sensing with a minimum sensitivity of 20 mm/s water flow. This work may provide a new manufacturing method and insight into future millimeter-scale soft sensors for bio-inspired robots. Full article
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14 pages, 3455 KiB  
Article
Miniature Mobile Robot Using Only One Tilted Vibration Motor
by Renjie Zhu, Yifan Zhang and Hongqiang Wang
Micromachines 2022, 13(8), 1184; https://doi.org/10.3390/mi13081184 - 27 Jul 2022
Cited by 3 | Viewed by 2960
Abstract
In miniature mobile robots, reducing the number of actuators can effectively reduce the size and weight of the robot. However, it is challenging to design a robot with as few actuators as possible without losing good motion performance. This work presented a simple-structured [...] Read more.
In miniature mobile robots, reducing the number of actuators can effectively reduce the size and weight of the robot. However, it is challenging to design a robot with as few actuators as possible without losing good motion performance. This work presented a simple-structured low-cost miniature mobile robot. It is driven by only a single tilted motor and yet is fully capable of being controlled to move forward and turn left or right on the ground. Based on the stick–slip mechanism, the robot’s motion is achieved by interplaying between the centrifugal force generated by the vibration motor tilted on the robot and the friction force of the robot. The robot’s speed can be controlled by regulating the magnitude and the period of the applied voltage. Finally, the robot can translate and rotate on the ground and follow various arbitrary paths. The prototype weighs only 11.15 g, costs $6.35, and is 20 mm in diameter and 25 mm in height. The proposed system is experimentally verified and demonstrates the controllability of the robot by the movement along a straight line, a circle, and more arbitrary paths. Full article
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12 pages, 17942 KiB  
Article
Design, Characterization, and Liftoff of an Insect-Scale Soft Robotic Dragonfly Powered by Dielectric Elastomer Actuators
by Yufeng Chen, Cathleen Arase, Zhijian Ren and Pakpong Chirarattananon
Micromachines 2022, 13(7), 1136; https://doi.org/10.3390/mi13071136 - 18 Jul 2022
Cited by 10 | Viewed by 3712
Abstract
Dragonflies are agile and efficient flyers that use two pairs of wings for demonstrating exquisite aerial maneuvers. Compared to two-winged insects such as bees or flies, dragonflies leverage forewing and hindwing interactions for achieving higher efficiency and net lift. Here we develop the [...] Read more.
Dragonflies are agile and efficient flyers that use two pairs of wings for demonstrating exquisite aerial maneuvers. Compared to two-winged insects such as bees or flies, dragonflies leverage forewing and hindwing interactions for achieving higher efficiency and net lift. Here we develop the first at-scale dragonfly-like robot and investigate the influence of flapping-wing kinematics on net lift force production. Our 317 mg robot is driven by two independent dielectric elastomer actuators that flap four wings at 350 Hz. We extract the robot flapping-wing kinematics using a high-speed camera, and further measure the robot lift forces at different operating frequencies, voltage amplitudes, and phases between the forewings and hindwings. Our robot achieves a maximum lift-to-weight ratio of 1.49, and its net lift force increases by 19% when the forewings and hindwings flap in-phase compared to out-of-phase flapping. These at-scale experiments demonstrate that forewing–hindwing interaction can significantly influence lift force production and aerodynamic efficiency of flapping-wing robots with passive wing pitch designs. Our results could further enable future experiments to achieve feedback-controlled flights. Full article
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10 pages, 4450 KiB  
Article
Design of a Biologically Inspired Water-Walking Robot Powered by Artificial Muscle
by Dongjin Kim, Minseok Gwon, Baekgyeom Kim, Victor M. Ortega-Jimenez, Seungyong Han, Daeshik Kang, M. Saad Bhamla and Je-Sung Koh
Micromachines 2022, 13(4), 627; https://doi.org/10.3390/mi13040627 - 15 Apr 2022
Cited by 7 | Viewed by 3439
Abstract
The agile and power-efficient locomotion of a water strider has inspired many water-walking devices. These bioinspired water strider robots generally adopt a DC motor to create a sculling trajectory of the driving leg. These robots are, thus, inevitably heavy with many supporting legs [...] Read more.
The agile and power-efficient locomotion of a water strider has inspired many water-walking devices. These bioinspired water strider robots generally adopt a DC motor to create a sculling trajectory of the driving leg. These robots are, thus, inevitably heavy with many supporting legs decreasing the velocity of the robots. There have only been a few attempts to employ smart materials despite their advantages of being lightweight and having high power densities. This paper proposes an artificial muscle-based water-walking robot capable of moving forward and turning with four degrees of freedom. A compliant amplified shape memory alloy actuator (CASA) used to amplify the strain of a shape memory alloy wire enables a wide sculling motion of the actuation leg with only four supporting legs to support the entire weight of the robot. Design parameters to increase the actuation strain of the actuator and to achieve a desired swing angle (80°) are analyzed. Finally, experiments to measure the forward speed and angular velocities of the robot are carried out to compare with other robots. The robot weighs only 0.236 g and has a maximum and average speed of 1.56, 0.31 body length per second and a maximum and average angular velocity of 145.05°/s and 14.72°/s. Full article
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