Department of Mechanical Engineering, KAIST, Daejeon 34141, Korea.
Lab Chip. 2017 Mar 14;17(6):1031-1040. doi: 10.1039/c6lc01405d.
Precise control over droplet position within a microchannel is fundamental to droplet microfluidic applications. This article proposes acoustothermal tweezer for the control of droplet position, which is based on thermocapillary droplet migration actuated by acoustothermal heating. The proposed system comprises an acoustothermal heater, which is composed of a slanted finger interdigital transducer patterned on a piezoelectric substrate and a thin PDMS membrane, and a PDMS microchannel. In the proposed system, droplets moving in a droplet microfluidic chip experience spatiotemporally varying thermal stimuli produced by acoustothermal heating and thus migrate laterally. In comparison to previous methods for droplet sorting, the acoustothermal tweezer offers significant advantages: first, the droplet position can be manipulated in two opposite directions, which enables bidirectional droplet sorting to one of three outlets downstream; second, precise control over the droplet position as well as improved droplet lateral displacement on the order of hundreds of micrometers can be achieved in a deterministic manner, thereby enabling multichannel droplet sorting; third, the PDMS microfluidic chip is disposable and thus can be easily replaced since it is attached to the substrate by reversible bonding, which allows the acoustothermal heater to be reused. Given these advantages, the proposed droplet sorting system is a promising droplet microfluidic lab-on-a-chip platform for tunable, on-demand droplet position control.
精确控制微通道内液滴的位置对于液滴微流控应用至关重要。本文提出了一种基于热毛细作用的声热镊子来控制液滴位置，该镊子利用声热加热驱动的热毛细液滴迁移来实现。所提出的系统包括一个声热加热器，它由一个倾斜的指状叉指换能器和一个薄的 PDMS 膜组成，以及一个 PDMS 微通道。在提出的系统中，在液滴微流控芯片中移动的液滴经历由声热加热产生的时变热刺激，从而横向迁移。与以前的液滴分选方法相比，声热镊子具有显著的优势：首先，可以在两个相反的方向上操纵液滴的位置，从而实现双向液滴分选到下游的三个出口之一；其次，可以以确定性的方式实现对液滴位置的精确控制以及提高液滴横向位移的精度，达到数百微米的量级，从而实现多通道液滴分选；第三，PDMS 微流控芯片是一次性的，因此可以很容易地更换，因为它通过可逆键合附着在基底上，这允许声热加热器重复使用。鉴于这些优势，所提出的液滴分选系统是一种有前途的用于可调、按需液滴位置控制的片上实验室液滴微流控平台。
