基于微泡共振的快速微流体声学混合方法研究

微流体在生物医学、化学工程等领域应用广泛,并具有重大意义.在预处理中,液体混合也是关键且最为必要的前序.为了提高微流控腔道内液体混合的效率,本文提出基于单微泡振动的声学混合器,通过微泡共振,产生声微流,声微流形成的剪切力将在流体中产生微扰动,实现液体的混合.设计了底面直径为40μm的微孔结构,由于液体表面张力作用形成微泡,在共振频率为165 kHz的压电换能器激励下,气泡发生共振产生声微流.通过对压电换能器输入不同能量,获取混合液体的最优参数,可在37.5 ms内实现混合效果,混合均匀度达到92.7%.本文设计的单微泡振动混合器结构简单、混合效率高、混合时间短、输入能量低,可为生物化学等方面的研究提供强有力的技术支撑.

Microbubble oscillation induced acoustic micromixing in microfluidic device

Microfluidic is of great significance for biomedical research and chemical engineering. The mixing of liquids is an essential and necessary procedure for the sample preparation. Due to the low Reynolds number, laminar flow is dominant in a microfluidic channel and it is difficult to mix the fluids in the microchannel quickly and effectively. To improve the mixing efficiency of the liquids in microfluidic channels, we develop an acoustic mixer based on single microbubble oscillation. By designing the cylinder structure on the bottom surface, when the fluid flows through cylinder structure with a diameter of 40 μm, the microbubble can be generated by the surface tension of the liquid. The device is fabricated by using standard soft lithography and the replica moulding technique, ensuring the stability and repeatability of the mixing. A piezoelectric transducer (PZT) with a resonant frequency of 165 kHz is attached to the polydimethylsiloxane microfluidic device on the glass substrate by ultrasound coupling gel. When the microbubble is excited by the PZT at a resonant frequency of 165 kHz, microbubble oscillates immediately. To verify whether ultrasound can induce microbubble cavitation, a passive cavitation detection system is established. The results show that the higher harmonics can be detected, indicating that the stable cavitation occurs. The microstreaming induced by the oscillating microbubble disturbs the fluid dramatically, achieving the mixture of liquids. Particle image velocimetry method is utilized to characterize the microstreaming, and a pair of counter-rotating vortices in the microchannel is detected. Furthermore, to test the performance of the device, the deionized water and rhodamine B are injected into the Y-shape microchannel. Relative mixing index is used to quantitatively analyze the mixing performance by measuring the grayscale values of the optical images. The results indicate that with the increase of the input power, mixing time can be shortened correspondingly. When the input power is 14.76 W, the mixing process is ultrafast, within 37.5 ms the high mixing uniformity can be achieved to be 92.7%. With the advantages of simple design, high efficient and ultrafast mixing, and low power consumption, this oscillating microbubble-based acoustic micromixer may provide a powerful tool for various biochemical studies and applications.