High-throughput micromixers based on acoustic streaming induced by surface acoustic wave

Abstract

Flow characteristics in microfluidic devices is naturally laminar due to the small channel dimensions. Mixing based on molecular diffusion is generally poor. In this article, we report the fabrication and characterization of active surface-acousticwave-driven micromixers which exploit the acoustic streaming effect to significantly improve the mixing efficiency. A side-by-side flow of water and fluorescent dye solution was driven by a syringe pump. Surface wave with a frequency of 13 MHz was launched perpendicular to the flow. The wave was generated by two designs of interdigitated electrodes on LiNbO 3 substrate: parallel electrodes and focusing electrodes. The mixing efficiency was observed to be proportional to the square of the applied voltage. Under the same applied voltage, the focusing type offers a better mixing efficiency. The fabrication of the micromixer is compatible to current technology such as soft lithography and deep reactive ion etching. Despite the high throughput and fast mixing time, the mixer design is simple and could be integrated into any microfluidic platform.

Transducer-Plane Streaming Patterns in Thin-Layer Acoustofluidic Devices

“…Understanding the driving mechanisms of acoustic streaming patterns within acoustofluidic devices is important in order to precisely control it for the enhancement or suppression of acoustic streaming for applications such as particle/cell manipulation [1-8], heat transfer enhancement [9][10][11][12], noncontact surface cleaning [13][14][15][16][17], microfluidic mixing [18][19][20][21][22][23][24][25][26][27], and transport enhancement [28][29][30][31][32][33][34][35].…”

“…INTRODUCTION Acoustic streaming is steady fluid motion driven by the absorption of acoustic energy due to the interaction of acoustic waves with the fluid medium or its solid boundaries. Understanding the driving mechanisms of acoustic streaming patterns within acoustofluidic devices is important in order to precisely control it for the enhancement or suppression of acoustic streaming for applications such as particle/cell manipulation [1-8], heat transfer enhancement [9-12], noncontact surface cleaning [13][14][15][16][17], microfluidic mixing [18][19][20][21][22][23][24][25][26][27], and transport enhancement [28][29][30][31][32][33][34][35].In most bulk micro-acoustofluidic particle and cell manipulation systems of interest, the acoustic streaming fields are dominated by boundary-driven streaming [36], which is associated with acoustic dissipation in the viscous boundary layer [37]. Theoretical work on boundary-driven streaming was initiated by Rayleigh [38], and developed by a series of modifications for particular cases [39][40][41][42][43][44], which have paved the fundamental understanding of acoustic streaming flows.…”

In-chip direct laser writing of a centimeter-scale acoustic micromixer

“…Typically, these mixers either excite a flow at the sidewalls of a microfluidic chamber [5][6][7] or excite a flow inside the chamber using a bubble. [8][9][10] In the case of homogeneous mixing, the chamber size is limited by the spatial extent of the induced flows, which subsequently limits the flow rate.…”

Vector network analyzer measurement of the amplitude of an electrically excited surface acoustic wave and validation by X-ray diffraction

“…11,12 It was found that the velocity of propagation of the domain walls depends on the amplitude of the SAW. In the area of microfluidics, recent research demonstrates that SAWs provide an effective means to manipulate fluids (fluid mixing, [13][14][15] translation, [16][17][18] jetting, 19 and atomization 20 ) and manipulate particles (handling, 21 focusing, 22 separation, 23,24 sorting, 25,26 concentration, [27][28][29][30] and reorientation 31 ) in lab-on-a-chip devices for applications in chemistry, biology, and medicine. The ability for a SAW to mix, translate, jet, and atomize droplets is dictated by its amplitude.…”