Numerical study of the effect of microchannel geometry on temperature gradient focusing using the Joule heating effect

We performed a numerical analysis to investigate the effect of microchannel geometry on the temperature gradient focusing (TGF) process using the Joule heating phenomenon. The governing equations were implemented into a quasi-one-dimensional (1-D) numerical model along a microchannel. The distributions of temperature, velocity, and concentration along the microchannel were predicted based on the numerical results. The narrower middle width and wider outside width of a channel with a fixed length improved the focusing performance. However, an excessively narrow middle width of the channel generates an improper high temperature that can cause problems, including sample denaturation and buffer solution boiling. Therefore, the geometry of the microchannel should be optimized to prevent these problems. We propose optimal microchannel widths for TGF using the ratio of the middle width and the outside width of the channel in order to improve focusing performance.