Nonlinear large deformation of acoustomechanical soft materials

An acoustomechanical theory of soft materials is proposed to account for the nonlinear large deformation of soft materials triggered by both the ultrasound waves and mechanical forces. This theory is formulated by employing the nonlinear elasticity theory of the soft material and the theory of acoustic radiation force, which takes into consideration of the combination loading of mechanical forces and acoustic inputs. While the propagation of acoustic wave depends on material configuration, the radiation force generated by wave propagation deforms the material configuration. This complex interaction reaches a steady state when the mechanical stress and the acoustic radiation stress are able to balance with the elastic deformation stress. The acoustomechanical theory is employed to characterize the acoustomechanical behaviors of thin soft material layers under different boundary conditions (e.g., equal-biaxial forces, uniaxial force, and uniaxial constraint). Prestretches arising from these boundary conditions are shown to play significant roles in affecting the acoustomechanical repsonse of soft material: the same material actuated from different prestretches and boundary conditions exhibits different stretch-stress relations. This novel functionality enables innovative design of acoustic sensors and actuators based on soft materials.