Flow Control through ultrasound-driven microbubble streaming

微流体技术是一种在微观尺度上操控气体和液体的技术，它正在给生命科学和化学工业带来革命性的变化。设备的小型化不仅旨在减少装置的尺寸，而且还减少了分析时间和化学试剂的数量。然而，由于涉及的尺度小，操纵微观流动成为一项复杂的任务。要克服的最困难的问题之一是在比分子扩散更短的时间尺度内实现物质的混合。本研究的目的是利用超声波激发微泡，在微流控芯片中诱导混沌平流。当一个微泡受到声激励时，它周围就会产生一股流。通过操纵这些复杂的流动，通过简单地操纵激励频率可以很容易地产生具有不同混合特性的不同流型。当微颗粒的固体悬浮液通过微通道时，可采用从最佳混合中获得的均质化来避免堵塞。此外，气泡流动产生的高应力可以用来破坏用于阻塞微流体通道中狭窄传导的颗粒团。为了测量、评价和优化流动的混合特性，将采用能够解决三维流动和大时间尺度的前沿实验速度测量技术。

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.