Nonlinear deformation and bifurcation of a soft cantilever induced by acoustic radiation force

Abstract

We theoretically and numerically demonstrate that the nonlinear bending deformation of a soft cantilever can be induced by acoustic radiation force when a plane ultrasonic wave impinges on it. The acoustic radiation force arises from the acoustic momentum change at the top and bottom interfaces of the soft cantilever, which is unevenly distributed at the interfaces and deformation curvature dependent. As the acoustic radiation force varies nonlinearly with the deformation of the cantilever, there exist multiple equilibrium configurations of the cantilever at a given incident ultrasonic wave (with fixed amplitude and frequency). This phenomenon is confirmed by both theoretical prediction and numerical simulation. Furthermore, by changing the pressure amplitude or the frequency of the incident wave, the deformation of the cantilever is able to switch from one equilibrium configuration to another equilibrium configuration discontinuously due to the snap-through instability. These nonlinear deformation and multistable switch performance of the system show promising potential applications in the fields of soft robotics, microfluidics and biomedicine and so on.