Acoustic actuators based on the resonance of an acoustic-film system applied to the actuation of soft robots

In this work, the coupling between an acoustic field and a soft film is studied and applied to the actuation of soft robots. First, the natural frequencies and modes for the acoustic-film coupling system are theoretically and numerically calculated. The steady-state solution of the acoustic-film coupling field is then obtained based on the Green's function method. By actuating standing waves or travelling waves in the resonant state of the acoustic-film system, two acoustic actuation methods are proposed for use in soft robots. Combining theoretical analysis and numerical simulations, it is shown that the soft robots that employed the two actuation methods have better kinetic and energetic performances owing to the resonant working state of the acoustic-film coupling system, compared to other types of soft robots, such as swimming, slithering, or quadruped gait robots. In addition, owing to the acoustic wave propagation in the soft robot body, the desired wave-like deformation for some types of soft robots can be easily achieved using local acoustic sources (e.g. built-in loudspeakers), which may significantly simplify the complex actuation or controlling system. The acoustic actuation mechanisms presented herein are expected to be applied to a large class of mobile soft robots requiring wave-like deformation.