Sharp-edge-based acoustofluidic chip for programmable pumping, mixing, cell focusing and trapping

TL;DR

This paper introduces a silicon-glass microfluidic chip that uses acoustically excited sharp edges to achieve programmable pumping, efficient mixing, and cell focusing or trapping, with broad frequency and flow rate control for bio-chemical applications.

Contribution

The work presents a multifunctional acoustofluidic chip capable of programmable flow, mixing, and cell manipulation, with detailed analysis and experimental validation of its acoustic and streaming behaviors.

Findings

Flow rates range from nL/min to μL/min and depend quadratically on voltage.

The device operates effectively across 80kHz-2MHz frequencies.

Finite element simulations agree well with experimental results.

Abstract

Precise manipulation of fluids and objects on the micro scale is seldom a simple task, but nevertheless crucial for many applications in life sciences and chemical engineering. We present a microfluidic chip fabricated in silicon-glass, featuring one or several pairs of acoustically excited sharp edges at side channels that drive a pumping flow throughout the chip and produce a strong mixing flow in their vicinity. The chip is simultaneously capable of focusing cells and microparticles that are suspended in the flow. The multifunctional micropump provides a continuous flow across a wide range of excitation frequencies (80kHz-2MHz), with flow rates ranging from nL/min to $\mu$L/min, depending on the excitation parameters. In the low-voltage regime, the flow rate depends quadratically on the voltage applied to the piezoelectric transducer, making the pump programmable. The behaviour in the system is elucidated with finite element method simulations, which are in good agreement with experimentally observed behaviour. The acoustic radiation force arising due to a fluidic channel resonance is responsible for the focusing of cells and microparticles, while the streaming produced by the pair of sharp edges generates the pumping and the mixing flow. If cell focusing is detrimental for a certain application, it can also be avoided by exciting the system away from the resonance frequency of the fluidic channel. The device, with its unique bundle of functionalities, displays great potential for various bio-chemical applications.