School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
Lab Chip. 2011 Apr 7;11(7):1396-402. doi: 10.1039/c0lc00421a. Epub 2011 Feb 18.
It is challenging to continuously concentrate sample solutes in microfluidic channels. We present an improved electrokinetic technique for enhancing microfluidic temperature gradient focusing (TGF) of sample solutes using combined AC and DC field induced Joule heating effects. The introduction of an AC electric field component services dual functions: one is to produce Joule heat for generating temperature gradient; the other is to suppress electroosmotic flow. Consequently the required DC voltages for achieving sample concentration by Joule heating induced TGF are reduced, thereby leading to smaller electroosmotic flow (EOF) and thus backpressure effects. As a demonstration, the proposed technique can lead to concentration enhancement of sample solutes of more than 2500-fold, which is much higher than the existing literature reported microfluidic concentration enhancement by utilizing the Joule heating induced TGF technique.
在微流道中连续浓缩样品溶质具有挑战性。我们提出了一种改进的电动技术，用于利用交流和直流电场诱导的焦耳加热效应增强微流控温度梯度聚焦（TGF）的样品溶质。引入交流电场分量具有双重功能：一是产生焦耳热以产生温度梯度；另一个是抑制电动流。因此，通过焦耳加热诱导 TGF 实现样品浓缩所需的直流电压降低，从而导致较小的电动流（EOF）和因此的背压效应。作为演示，所提出的技术可以使样品溶质的浓度增强超过 2500 倍，这远远高于现有文献报道的利用焦耳加热诱导 TGF 技术的微流控浓度增强。
