A Self-Walking Actuator Inspired By Caterpillars

Scientists have designed an actuator that can form complex three-dimensional structures in response to differing levels of humidity.

AsianScientist (Jul. 13, 2015) – Inspired by caterpillars, researchers have created a well-defined hydroresponsive self-folding device that can fold into complex three-dimensional structures and can perform active movement on surfaces with a roughness gradient. Their results have been published in Small.

In nature, plants and muscular organs have the ability to convert physical or chemical signals into macroscopic movements. For example, some can form complex shapes in response to specific external stimuli in the environment.

In the present study, Professor Zhou Feng and colleagues at the Lanzhou Institute of Chemical Physics of the Chinese Academy of Sciences have created a caterpillar–mimetic bilayer actuator based on a wrinkled polydimethylsiloxane (PDMS) elastomer decorated with a hydroresponsive polyelectrolyte brush.

The actuator can quickly fold into complex three-dimensional structures upon a change in relative humidity of the surrounding air. Upon increasing the humidity or immersed in water, the brush swells and the resulting lateral pressure leads to a bending movement of the rubber within a fraction of a second.

The direction of bending can be manipulated by introducing a pattern of wrinkles on the PDMS substrate. And some unique structures such as helicoid and gradient which are seldom reported in the case of bilayered devices can be obtained.

The actuation is fast, reversible, reproducible and robust. When the environmental humidity is repeatedly cycled up and down, the small device walks on a surface with a roughness gradient, which is reminiscent of the muscle-like movements.

It is hoped that that the design can be used in a variety of applications where programmable shape changes are needed, including actuators, cell encapsulation, artificial muscles and soft robotics.

The article can be found at: Li et al. (2015) Caterpillar-Inspired Design and Fabrication of A Self-Walking Actuator with Anisotropy, Gradient, and Instant Response.


Source: Chinese Academy of Sciences.
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