Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA.
Lab Chip. 2012 Aug 7;12(15):2736-42. doi: 10.1039/c2lc21123h. Epub 2012 May 29.
This paper presents experimental results demonstrating the feasibility of high frequency ultrasonic sensing and sorting for screening single oleic acid (lipid or oil) droplets under continuous flow in a microfluidic channel. In these experiments, hydrodynamically focused lipid droplets of two different diameters (50 μm and 100 μm) are centered along the middle of the channel, which is filled with deionized (DI) water. A 30 MHz lithium niobate (LiNbO(3)) transducer, placed outside the channel, first transmits short sensing pulses to non-invasively determine the acoustic scattering properties of the individual droplets passing through the beam's focus. Integrated backscatter (IB) coefficients, utilized as a sorting criterion, are measured by analyzing the received echo signals from each droplet. When the IB values corresponding to 100 μm droplets are obtained, a custom-built LabVIEW panel commands the transducer to emit sinusoidal burst signals to commence the sorting operation. The number of droplets tested for the sorting is 139 for 50 μm droplets and 95 for 100 μm droplets. The sensing efficiencies are estimated to be 98.6% and 99.0%, respectively. The sorting is carried out by applying acoustic radiation forces to 100 μm droplets to direct them towards the upper sheath flow, thus separating them from the centered droplet flow. The sorting efficiencies are 99.3% for 50 μm droplets and 85.3% for 100 μm droplets. The results suggest that this proposed technique has the potential to be further developed into a cost-effective and efficient cell/microparticle sorting instrument.
本文展示了实验结果，证明了在微流道中连续流动条件下，利用高频超声传感和分选技术筛选单油酸（脂质或油）液滴的可行性。在这些实验中，两种不同直径（50μm 和 100μm）的液滴在充满去离子水的微通道中间被水动力聚焦。一个 30MHz 的铌酸锂（LiNbO(3)）换能器放置在通道外部，首先发送短的传感脉冲，以非侵入式方式确定穿过波束焦点的单个液滴的声学散射特性。将积分回波（IB）系数用作分选标准，通过分析来自每个液滴的接收回波信号进行测量。当获得对应于 100μm 液滴的 IB 值时，一个定制的 LabVIEW 面板命令换能器发射正弦突发信号以启动分选操作。分选的测试液滴数量为 50μm 液滴 139 个，100μm 液滴 95 个。传感效率分别估计为 98.6%和 99.0%。分选通过对 100μm 液滴施加声辐射力来进行，将其引导到上鞘流中，从而将其与中心液滴流分离。50μm 液滴的分选效率为 99.3%，100μm 液滴的分选效率为 85.3%。结果表明，该技术具有进一步开发成为一种具有成本效益和高效率的细胞/微颗粒分选仪器的潜力。
