Modeling of hysteretic paths in cyclic deflation-inflation of spherical shells: application to the design of artificial microswimmers

Flows at the microscale are intuitively associated with being slow, laminar, and controlled by dissipation mechanisms. This makes transport mechanisms particularly inefficient, compared to their inertia-driven counterparts at larger scales. Examples include the mixing, sorting and swimming of small quantities or objects. This project proposes a paradigm shift: an ultrasound-driven buckling instability of geometrically simple elastic objects (hollow spherical shells) will make inertial fluid mechanics enter the microscopic realm. The instability can transform potential energy provided by an ultrasound signal into kinetic energy at a rate of at least thousands of times per second. The objective of the project is to gain a fundamental understanding of this novel mechanism by analyzing the interaction between the forcing ultrasound signal, hydrodynamics, shell mechanics, gas pressure and shape dynamics. Within the present project, these questions will be addressed through a theoretical modeling that will be developed in collaboration with Douglas Holmes, at Boston University.