Soft material actuation by atomization

摘要

Abstract Soft robotics are receiving great attention due to its compliant nature and its potential for achieving high degree-of-freedom motions, which are essential for mimicking bioinspired systems. Various methods have been developed to actuate soft materials, ranging from pneumatic actuation to implementing phase transformation. However, techniques that involve fluid pressure require tethered tubes and external compressors, whereas phase transformation generally relies on high temperature changes. In this study, a novel method of actuation that employs ultrasonic-atomization-induced phase transformation of liquid embedded in cavities within soft materials is achieved. In short, atomization is achieved by applying ultrasonic waves on a layer of liquid to create capillary waves at the surface, where small droplets are then ejected from the crests. Small droplets generated by atomization drastically increase the evaporation rate without the need to increase the temperature to boiling. In this study, hollow structures were fabricated with a soft elastomer that were partially filled with ethanol. Ultrasonic waves were propagated through a wall of the structure to atomize the embedded ethanol. Atomizing the embedded ethanol demonstrated as high as ∼10 times faster actuation rates as compared to evaporating bulk ethanol through heating. The results showed that actuation performance could be controlled by adjusting the voltage and frequency of the signal exciting the transducer. Furthermore, repetitive back-and-forth movement without having to cool the structure was successfully validated.