Session: 12-28-01: Functional Soft Composites - Design, Mechanics, and Manufacturing

Paper Number: 147260

147260 - Electrothermal Actuation for Soft Robotics 

Soft robots have found a wide range of applications in biomedical engineering, surgical assistance, and active prosthetics, to name a few. Among all the actuation methods for soft robotics, electrothermal actuation shows appealing features such as programmable operation, lightweight, low actuation voltage, and potential for untethered operation.

One major challenge for electrothermal actuation is the relatively low speed. Here we first introduce a bimorph thermal actuator, based on a silver nanowire/polydimethylsiloxane (AgNW/PDMS) composite, with snap-through instability to achieve fast actuation. The snap-through instability is introduced by applying an offset displacement to the passive ribbon. The effects of thermal conductivity of the AgNW/PDMS composite, offset displacement, and actuation frequency on the actuator performance have been studied. The snap-through instability significantly increases the actuation speed, up to 10 times that without the instability. We demonstrated a soft crawling robot with high locomotion speed (over one body length per second at the frequency ~0.5 Hz). We also developed a biomimetic Venus flytrap providing fast opening and closing speed (up to 24 mm/s).

Another challenge for soft robots is to achieve bidirectional and programmable locomotion. Here, we report a bioinspired crawling robot that mimics the caterpillar locomotion with multiple crawling modes, controlled by joule heating of a patterned soft heater consisting of AgNW networks in a liquid crystal elastomer (LCE)-based thermal bimorph actuator. With distributed heating pattern and switchable conducting channels, different temperature and curvature distribution are achieved, enabling bidirectional locomotion as a result of the adjustable friction competition between the front and rear end with the ground. The bidirectional actuation modes, the crawling speed, and the capability of passing through obstacles with limited space are investigated with experiments and finite element analyses.

The third challenge is the steering motion of soft robots. The inching motion and crawling motion of caterpillars have been widely studied in the design of soft robots while the steering motion with local bending control remains challenging. The modular origami unit offers an excellent building block for mimicking the segmented caterpillar body. Here, we report a modular soft Kresling origami crawling robot enabled by electrothermal actuation. A compact and lightweight Kresling structure is designed, fabricated, and characterized with integrated thermal bimorph actuators consisting of LCE and polyimide layers. With the modular design and programmable actuation, a multi-unit caterpillar-inspired soft robot composed of active units and passive units is developed for bidirectional locomotion and steering locomotion with precise curvature control. Finally, we demonstrate the modular design of the Kresling origami robot with an active robotic module picking up cargo and assembling with another robotic module to obtain steering function. The concept of modular soft robots can provide insight into the future soft robots that can grow, repair, and evolve.

Presenting Author: Shuang Wu North Carolina State University

Presenting Author Biography: Dr. Shuang Wu is a postdoctoral research scholar at North Carolina State University. He obtained his Bachelor's degree from Huazhong University of Science and Technology, his Master's degree in mechanical engineering from Zhejiang University, and his PhD in mechanical engineering from North Carolina State University. Currently, he is focusing on soft electronics and soft robotics in his role as a postdoctoral research scholar.

Authors:

Shuang Wu North Carolina State University
Jennifer Lee North Carolina State University
Yong Zhu North Carolina State University