Kates Brian, Ren Carolyn L
Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
Electrophoresis. 2006 May;27(10):1967-76. doi: 10.1002/elps.200500784.
IEF is a high-resolution separation method taking place in a medium with continuous pH gradients, which can be set up by applying electrical field to the liquid in a diverging microchannel. The axial variation of the channel cross-sectional area will induce nonuniform Joule heating and set up temperature gradient, which will generate pH gradient when proper medium is used. In order to operationally control the thermally generated pH gradients, fundamental understanding of heat transfer phenomena in microfluidic chips with diverging microchannels must be improved. In this paper, two 3-D numerical models are presented to study heat transfer in diverging microchannels, with static and moving liquid, respectively. Through simulation, the temperature distribution for the entire chip has been revealed, including both liquid and solid regions. The model for the static liquid scenario has been compared with published results for validation. Parametric studies have showed that the channel geometry has significant effects on the peak temperature location, and the electrical conductivity of the medium and the wall boundary convection have effects on the generated temperature gradients and thus the generated pH gradients. The solution to the continuous flow model, where the medium convection is considered, shows that liquid convection has significant effects on temperature distribution and the peak temperature location.
等电聚焦是一种在具有连续pH梯度的介质中进行的高分辨率分离方法，该梯度可通过在发散微通道中对液体施加电场来建立。通道横截面积的轴向变化会引起不均匀的焦耳热并建立温度梯度，当使用合适的介质时，这将产生pH梯度。为了在操作上控制热产生的pH梯度，必须加深对具有发散微通道的微流控芯片中传热现象的基本理解。本文提出了两个三维数值模型，分别研究静态和流动液体情况下发散微通道中的传热。通过模拟，揭示了整个芯片的温度分布，包括液体和固体区域。已将静态液体情况的模型与已发表的结果进行比较以进行验证。参数研究表明，通道几何形状对峰值温度位置有显著影响，介质的电导率和壁边界对流对产生的温度梯度以及由此产生的pH梯度有影响。考虑介质对流的连续流动模型的解表明，液体对流对温度分布和峰值温度位置有显著影响。
