Characterization of Soft Actuation Through Ultrasonic Atomization

Abstract

Most biological systems fully take advantage of their soft tissues by quickly reacting and interacting with the environment. This exceptional performance is possible due to flexible muscles that can bend and contract in multiple degrees-of-freedom. Since traditional robots with rigid components cannot mimic these movements, soft robotic systems fabricated from flexible elastomers are starting to receive much attention. Similarly, developing actuation techniques that can control the movement of these soft materials in multiple degrees-of-freedom is also crucial. This study proposes a new soft actuation mechanism through the use of ultrasonic atomization and small piezoelectric transducers. Unlike conventional pneumatic-based systems, this soft structure is completely untethered, which can be actuated by simply placing it above an ultrasonic transducer. First, a hollow structure was fabricated by pouring uncured elastomer into a 3D-printed mold. Second, the structure was partially filled with a small amount of liquid and placed above a piezoelectric disc. Then, exciting the transducer generated ultrasonic waves that propagated through the wall of the structure. When the amplitude of the ultrasonic wave was high enough, the liquid inside the structure was atomized and ejected small droplets inside the closed, soft chamber. These droplets rapidly evaporated and deformed the soft structure. In this work, the experimental results were compared with finite element modeling to characterize the ultrasonic-atomization-induced soft structure actuation.