Cavity optomechanics on a microfluidic resonator with water and viscous liquids

TL;DR

This paper demonstrates the first optomechanical actuation of a microfluidic system with liquids, using a hollow bubble resonator to excite vibrations in liquids with high viscous dissipation, enabling new studies of non-solid matter phases.

Contribution

It introduces a novel microfluidic optomechanical device that can excite vibrations in liquids, overcoming previous limitations due to acoustic impedance and radiation losses.

Findings

First demonstration of optomechanical actuation in a microfluidic system with liquids.

Able to excite 100-MHz vibrations in viscous liquids using low optical power.

Measured density changes in liquids via vibration frequency shifts.

Abstract

Currently, optical- or mechanical-resonances are commonly used in microfluidic research. However, optomechanical oscillations by light pressure were not shown with liquids. This is because replacing the surrounding air with water inherently increases the acoustical impedance and hence the associated acoustical radiation-losses. Here, we bridge between microfluidics and optomechanics by fabricating hollow bubble resonators with liquid inside and optically exciting 100-MHz vibrations with only mW optical-input power. This constitutes the first time that any microfluidic system is optomechanically actuated. We further prove the feasibility of microfluidic optomechanics on liquids by demonstrating vibrations on organic fluids with viscous-dissipation higher than blood viscosity while measuring density changes in the liquid via the vibration frequency shift. Our device will enable using cavity optomechanics for studying non-solid phases of matter.