Ultra-sound activated inertial microrobots – Usain-BOT

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.
Our 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 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. Thereby we will investigate how fluid can be propelled in the vicinity of the shell, in a fast, controllable, and efficient way. For the microswimmer application, this should lead to a propulsion mechanism which is orders of magnitude faster than current techniques.
The combination of a powerful flow generation mechanism realized by simple-to-produce microscopic objects (hollow shells) and powered by a cheap and controllable technique (ultrasound) opens a multitude of further applications, including targeted drug delivery. The foundation of which will be laid in the present project by an interdisciplinary collaboration between experiments, theoretical modeling, and simulations of the full 3D fluid-structure interaction.