Acoustofluidic Microbioreactor Using Surface Acoustic Wave-induced Acoustic Streaming Flow

Microbioreactors have been widely utilized as an alternative to conventional benchtop reactors, since the miniaturized platforms offer advantages including reduced sample volume and homogeneous microenvironments. Here, we proposed an acoustofluidic microbioreactor based on surface acoustic wave (SAW)-induced acoustic streaming flow (ASF). The SAW-induced ASF, which originates from the wave attenuation in a fluid, allows rapid mixing and heat transfer for enhanced mass and heat transfer within the sample fluid. We conducted thorough numerical and experimental investigations on the acousto-hydrodynamics and heat transfer phenomena to find an optimal frequency in the prescribed cylindrical microwell. We found that the homogenous chemical concentration and temperature distributions within the fluid were rapidly achieved by the SAW-induced ASF in the proposed device. For proof-of-concept demonstration of practical applicability, we cultured Escherichia coli as a model cell using the proposed acoustofluidic microbioreactor. From comparative evaluation with conventional platforms including a shaker incubator and a microplate shaker, we confirmed that the bacteria growth rate was enhanced in the proposed acoustofluidic microbioreactor due to the high homogeneity in the chemical concentration and temperature by the acoustic agitation, without any moving mechanical components. We expect that the proposed ASF-based microbioreactor can be broadly utilized for various biological applications that require homogeneous mixing and temperature gradient within a reaction medium.