The use of acoustic streaming in Sub-micron particle sorting

Abstract

The lack of personal particulate matter (PM) monitoring technique hinders the knowledge of the negative health impacts caused by inhaling PM. Acoustophoresis has a potential to produce miniature particle sorters that can be carried inside human’s breath zone. Micron particles can be manipulated by Acoustic Radiation Force (ARF), but sub-micron particles can hardly be directed due to Acoustic Streaming Effect (ASE). The purpose of this study is to examine the feasibility of sorting sub-micron particles using ASE. In this study, a 2 D numerical model is used to simulate the movement of sub-micron particles, ranging from 0.1 µm to 0.9 µm in diameter with 0.1 µm step size, suspended in a microchannel. Since tiny particles circulate according to the streaming pattern, which depends on the geometry of the container, the effect of the microchannel’s cross-sectional shape on particle movement is investigated, from rectangular to non-rectangular. Results found that sub-micron particles are characterized as either ARF-dominant or ASE-dominant. ARF-dominant particles stop at the pressure node and sidewalls, while ASE-dominant particles are trapped by the streaming flow inside a certain area defined by the particle size. Larger ASE-dominant particles move in a narrower region close to the sidewalls; smaller particles occupy a wider area. Since ASE-dominant particles can be directed outside the settling location of ARF-dominated particles, separating them can reach 98.9% purity in a non-rectangular microchannel. Most importantly, separating ASE-dominant particles of different sizes is shown possible using a triangular microchannel. The findings imply that ASE can be the mechanism for sub-micron particle sorting.

Copyright © 2021 American Association for Aerosol Research

EDITOR:

• Jonathan P. Reid

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Hong Kong Special Administrative Region Government under Collaborative Research Fund (CRF) (project no. C7025-16G) and General Research Fund (GRF) (project no.16206918).