ASIC and System State Key Laboratory, School of Microelectronics, Fudan University, Shanghai 200433, P. R. China.
Viral Hemorrhagic Fevers Research Unit, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai 200031, P. R. China.
Anal Chem. 2023 Apr 18;95(15):6253-6260. doi: 10.1021/acs.analchem.2c03877. Epub 2023 Apr 5.
Acoustic mixing of droplets is a promising way to implement biosensors that combine high speed and minimal reagent consumption. To date, this type of droplet mixing is driven by a volume force resulting from the absorption of high-frequency acoustic waves in the bulk of the fluid. Here, we show that the speed of these sensors is limited by the slow advection of analyte to the sensor surface due to the formation of a hydrodynamic boundary layer. We eliminate this hydrodynamic boundary layer by using much lower ultrasonic frequencies to excite the droplet, which drives a Rayleigh streaming that behaves essentially like a slip velocity. At equal average flow velocity in the droplet, both experiment and three-dimensional simulations show that this provides a three-fold speedup compared to Eckart streaming. Experimentally, we further shorten a SARS-CoV-2 antibody immunoassay from 20 min to 40 s taking advantage of Rayleigh acoustic streaming.
液滴的声学混合是实现将高速和最小试剂消耗相结合的生物传感器的一种很有前途的方法。迄今为止，这种类型的液滴混合是由在流体主体中吸收高频声波产生的体积力驱动的。在这里，我们表明，由于形成流体动力学边界层，传感器的速度受到由于分析物缓慢向传感器表面的对流的限制。我们通过使用低得多的超声波频率来激发液滴来消除这种流体动力学边界层，这会产生瑞利流，其行为基本上类似于滑移速度。在液滴中具有相等的平均流速的情况下，实验和三维模拟均表明，与埃克特流相比，这提供了三倍的速度提升。在实验中，我们进一步利用瑞利声流将 SARS-CoV-2 抗体免疫分析从 20 分钟缩短至 40 秒。
