Bundled Liquid Crystal Elastomer Actuators with Integrated Cooling for Mesoscale Soft Robots
Anoush Sepehri, Sukjun Kim, Devyansh Agrawal, Hannah Yared, Gaoweiang Dong, Shengqiang Cai, Tania K. Morimoto
AI summary
Problem
Thermal soft actuators typically face a difficult trade-off between generating high force and achieving fast response speeds due to slow passive cooling. This limitation restricts their practical use in portable mesoscale soft robots and wearable devices.
Approach
The researchers bundled multiple thin LCE units in parallel to maximize surface area and integrated a compact air vent to force cross-flow cooling, dramatically speeding up heat dissipation. They also developed an analytical electro-thermo-mechanical model to systematically guide actuator design.
Key results
- Active cooling accelerated response speed by over 400% compared to passive cooling
- Validated electro-thermo-mechanical model accurately predicts force and cooling rates
- Inchworm-inspired robot achieves locomotion at 6 body lengths per minute
- Textile forearm cuff delivers 4 mm of haptic skin stretch with 1-second cooling
Why it matters
Enables practical, portable soft robotics and wearable haptics by providing a scalable method to rapidly cool high-force thermal actuators without bulky equipment.
Abstract
Liquid crystal elastomer (LCE) is a promising material to develop thermally-driven soft actuators due to its high force density, large elastic strain limit, and mechanically programmable nature. However, the complex trade-off between the force generated and the response speed (i.e., cooling rate), along with the lack of systematic design guidelines necessary to design such actuators using LCE, has significantly limited its widespread adoption for soft robotic applications at the mesoscale (cm-scale). In this work, we developed thermally- driven soft actuators by bundling LCE units with integrated cooling that increased the response speed by over 400% when compared to relying only on passive cooling. We developed and experimentally validated an electro-thermo-mechanical model to predict the force and cooling rate of our actuator and established systematic design guidelines to build our actuators for different soft robotic applications. Using our proposed guidelines, we present an inchworm inspired locomotion robot with a top speed of 6 body lengths per minute. We also present a textile forearm cuff with integrated haptic feedback that can provide up to 4 mm of skin stretch feedback with a cooling rate of 1 second. Overall, the presented actuator, experimental results, and design guidelines expand the potential use cases for thermally-driven actuators in soft robotic applications at the mesoscale.