Flow Control through ultrasound-driven microbubble streaming

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Microfluidics, the manipulation of gasses and liquids on the micro-scale, is revolutionizing the life sciences and the chemical industry. The miniaturization of the devices not only intends to reduce the size of the setups, but also to reduce the time for analysis, and the amount of chemical reagents. However, due to the small scales involved, manipulation of microscopic flows becomes a complex task. One of the most difficult problems to overcome is to achieve mixing of substances intimes scales shorter than those achieved by molecular diffusion. The aim of the current proposal is to induce chaotic advection in the microfluidic chips by exciting microbubbles with ultrasoundwaves. When a microbubble is acoustically excited a streaming flow is generated around it. By manipulating these complex flows different flow patterns with different mixing properties can be easily generated by simply manipulating the excitation frequencies. The homogenization obtained from an optimal mixing can be employed to avoid clogging when a solid suspension of microparticles passes through the microchannel. Furthermore, the high stresses generated by thebubble-streaming flow can be employed to break particle clusters that use to block narrow conducts in microfluidics channels. In order to measure, evaluate and optimize the mixing properties of the flows, front-edge experimental velocimetry techniques able to solve three dimensional flows and a large range of time scales will be employed.