Joule heating and its effects on electroosmotic flow in microfluidic channels

Joule heating is resulted from inevitable volumetric heating when an electric field is applied across conducting media and it would impose limitations to the performance of electrokinetic microfluidic devices. In this paper, the Joule heating and its effects on electroosmotic flow (EOF) in PDMS microfluidic channels are reported. 3D numerical simulation of the Joule heating induced temperature field and its effects on the EOF and electrophoretic transport of solutes in microchannels was performed. Experiments were carried out to verify the proposed models and the developed numerical code. A Rhodamine B based thermometry technique was used to measure the solution temperature distributions in PDMS microfluidic channels. The micro particle image velocimetry (micro-PIV) technique was used to characterize the velocity profiles of the EOF under the influence of Joule heating. The numerical simulations were compared with the experimental results, and reasonable agreement is found. Both the numerical simulations and the experimental results show that the presence of the Joule heating causes the EOF velocity to deviate from its normal “plug-like” profile; the EOF velocity exhibits a concaved shape in the hydrodynamically developing region and a convex (parabolic) pattern in the fully developed region.