Control and ultrasonic actuation of a gas-liquid interface in a microfluidic chip

TL;DR

This paper presents a microfluidic chip capable of controlling a gas-liquid interface using pressure differences and ultrasonic excitation, with detailed analysis of interface behavior, flow dynamics, and potential applications in particle transport and mixing.

Contribution

It introduces a novel microfluidic chip design that enables precise control of gas-liquid interfaces via pressure and ultrasonic methods, including experimental and theoretical analysis.

Findings

Different micro-geometries vary in anchoring efficiency.

Critical pressures for interface movement are experimentally validated.

Ultrasonic excitation induces traveling and standing waves, enabling flow control.

Abstract

This article describes the design and manufacturing of a microfluidic chip, allowing for the actuation of a gas-liquid interface and of the neighboring fluid. A first way to control the interface motion is to apply a pressure difference across it. In this case, the efficiency of three different micro-geometries at anchoring the interface is compared. Also, the critical pressures needed to move the interface are measured and compared to theoretical result. A second way to control the interface motion is by ultrasonic excitation. When the excitation is weak, the interface exhibits traveling waves, which follow a dispersion equation. At stronger ultrasonic levels, standing waves appear on the interface, with frequencies that are half integer multiple of the excitation frequency. An associated microstreaming flow field observed in the vicinity of the interface is characterized. The meniscus and associated streaming flow have the potential to transport particles and mix reagents.