Ultrasound-propelled nano- and microspinners

TL;DR

This study investigates how nonhelical nano- and microparticles can be propelled and made to spin using ultrasound, revealing their potential as persistent nano- and microspinners driven by acoustic forces.

Contribution

The paper introduces the concept of ultrasound-driven nano- and microspinners based on shape-induced rotation, supported by acoustofluidic simulations and analysis of flow fields and forces.

Findings

Flow field around particles depends on orientation.

Orientation-averaged propulsion force is zero.

Orientation-averaged propulsion torque is nonzero.

Abstract

We study nonhelical nano- and microparticles that, through a particular shape, rotate when they are exposed to ultrasound. Employing acoustofluidic computer simulations, we investigate the flow field that is generated around these particles in the presence of a planar traveling ultrasound wave as well as the resulting propulsion force and torque of the particles. We study how the flow field and the propulsion force and torque depend on the particles' orientation relative to the propagation direction of the ultrasound wave. Furthermore, we show that the orientation-averaged propulsion force vanishes whereas the orientation-averaged propulsion torque is nonzero. Thus, we reveal that these particles can constitute nano- and microspinners that persistently rotate in isotropic ultrasound.