Reversible vertical positioning of acoustically levitated particle using a spiral reflector

TL;DR

This paper introduces a mechanically actuated spiral reflector that enables reversible vertical positioning of acoustically levitated particles, eliminating the need for complex electronic control.

Contribution

It demonstrates a novel, mechanically simple method for bidirectional vertical particle translation using a rotating spiral reflector with stable confinement.

Findings

Achieved approximately 0.58λ vertical displacement per revolution.

Maximum height of 3.18λ with stable radial confinement.

Validated through experimental and numerical results.

Abstract

Dynamic positioning in acoustic levitation typically depends on active control of the transducers phases, which necessitates complex driving electronics. While mechanically actuated reflectors offer a simpler alternative, achieving reversible transport along the vertical axis solely through mechanical actuation remains challenging. Here, we demonstrate vertical particle translation using a rotating spiral reflector with a half-wavelength pitch. With the rotation axis laterally offset relative to the acoustic focus, the spiral surface functions as a series of translating slopes. Experimental and numerical results confirm stable, bidirectional transport, yielding a vertical displacement of approximately $0.58\lambda$ per revolution and a maximum height of $3.18\lambda$, with radial confinement maintained within $0.24\lambda$. This approach provides a cost-effective solution for non-contact sample handling without active phase control.