A Lesson from Plants: High-Speed Soft Robotic Actuators.

Richard Baumgartner,Soo Jin Adrian Koh,Guoyong Mao,Siegfried Bauer,Choon Chiang Foo,Josef M Stadlbauer,Christoph Keplinger,Rainer Kaltseis,Alexander Kogler,Zhigang Suo,Melanie Baumgartner,Martin Kaltenbrunner,Nikita Arnold

doi:10.1002/advs.201903391

Abstract

Rapid energy‐efficient movements are one of nature's greatest developments. Mechanisms like snap‐buckling allow plants like the Venus flytrap to close the terminal lobes of their leaves at barely perceptible speed. Here, a soft balloon actuator is presented, which is inspired by such mechanical instabilities and creates safe, giant, and fast deformations. The basic design comprises two inflated elastomer membranes pneumatically coupled by a pressurized chamber of suitable volume. The high‐speed actuation of a rubber balloon in a state close to the verge of mechanical instability is remotely triggered by a voltage‐controlled dielectric elastomer membrane. This method spatially separates electrically active and passive parts, and thereby averts electrical breakdown resulting from the drastic thinning of an electroactive membrane during large expansion. Bistable operation with small and large volumes of the rubber balloon is demonstrated, achieving large volume changes of 1398% and a high‐speed area change rate of 2600 cm2 s−1. The presented combination of fast response time with large deformation and safe handling are central aspects for a new generation of soft bio‐inspired robots and can help pave the way for applications ranging from haptic displays to soft grippers and high‐speed sorting machines.

Highlights

We build our system of coupled balloons by mounting a dielectric elastomer membrane (VHB) as trigger actuator (TA) and a rubber balloon featuring low viscoelasticity as high-speed actuator (HSA) on a chamber of suitable volume
The operation of the HSA is separated into the following steps: The initial pressure of the system is set to pA of state A, slightly above the verge of instability of the rubber balloon in state E to enable electrically triggered, giant deformation
Consisting of an electrically active and passive part, this actuator can be operated in a safe regime, far away from the electrical breakdown (EB) voltage of the dielectric elastomer

Summary

Introduction

Quick and large movements are keenly sought-after for applications in rigid and soft robotics, industrial automation, and modern prosthetics.[1,2,3,4,5] In recent years, the development of artificial muscles that mimic the basic function of human and animal musculature has gained an importance due to its wide range of potential applications.[6] But there are examples in which direct muscle action alone cannot be responsible for the rapid movement. The jaw muscles of hummingbirds are not strong enough to close the beak in the observed short amount of time. Hummingbirds are able to bend their lower jaw and use a controlled elastic instability to rapidly snap it from the open to the closed position.[7] Completely without muscle

Results

Discussion

Conclusion