Acoustic microstreaming for biological sample mixing enhancement

A mixing technique based on bubble-induced acoustic microstreaming principle was developed. A mixer consists of a piezoelectric disk that is attached to a reaction chamber, which has a set of air bubbles with desirable size trapped in the. solution. Fluidic experiments showed that air bubbles resting on a solid surface and set into vibration by the sound field generated circulatory flows, resulting in global convection flows and thus rapid mixing. The time to fully mix a 100 /spl mu/L chamber is significantly reduced from hours (diffusion-only) to tens of seconds. CFD modeling showed that the induced flowfield and thus degree of mixing strongly depends on bubble positions. Immuno-magnetic cell capture experiments showed acoustic microstreaming provided efficient mixing of bacterial cell (E. coli K12) matrix suspended in blood with magnetic capture beads, resulting highly effective immuno-magnetic cell capture. Bacterial viability assay experiments showed that acoustic microstreaming has a relatively low shear strain field since the blood cells and bacteria remained intact after mixing: Acoustic microstreaming has many advantages over most existing chamber micromixing techniques, including simple apparatus, ease of implementation, low power consumption (2 mW), and low cost.