Assessment of Joule heating and its effects on electroosmotic flow and electrophoretic transport of solutes in microfluidic channels

Abstract

Joule heating is inevitable when an electric field is applied across a conducting medium. It would impose limitations on the performance of electrokinetic microfluidic devices. This article presents a 3-D mathematical model for Joule heating and its effects on the EOF and electrophoretic transport of solutes in microfluidic channels. The governing equations were numerically solved using the finite-volume method. Experiments were carried out to investigate the Joule heating associated phenomena and to verify the numerical models. A rhodamine B-based thermometry technique was employed to measure the solution temperature distributions in microfluidic channels. The microparticle image velocimetry technique was used to measure the velocity profiles of EOF under the influence of Joule heating. The numerical solutions were compared with experimental results, and reasonable agreement was found. It is found that with the presence of Joule heating, the EOF velocity deviates from its normal "plug-like" profile. The numerical simulations show that Joule heating not only accelerates the sample transport but also distorts the shape of the sample band.

Joule heating effects on electroosmotic flow in insulator‐based dielectrophoresis

“…(5). This effect is more pronounced in the 500 V DC case, and is consistent with the temperature distribution in capillary or microchip-based electrophoresis, where the Joule heatingcaused high temperature plateau in the main body of the capillary or microchannel shifts toward the outlet reservoir due to electroosmotic effect [55,56]. Further decreasing the DC voltage to 50 V while increasing the AC voltage to 550 V, we observed electrothermal fluid circulations at both the downstream and the upstream ends of the channel constriction as demonstrated in Fig.…”

“…Under a 600 V DC voltage, there are no apparent disturbances to both the observed pathlines (bottom) and the predicted streamlines (top) in Fig. 3A as compared with the previously reported electroosmotic flow profiles in the presence of Joule heating [50,55,56]. However, when the DC voltage was decreased to 100 V and a 500 V AC voltage was applied to maintain the total magnitude, a pair of small counter-rotating circulations was observed to occur at the downstream end of the constriction in Fig.…”

“…[49] and those used in other studies [50,56,57], which indicate that Joule heating of the fluid was dissipated mainly through the bottom glass slide in our microchannel. It is because glass has a much higher thermal conductivity than PDMS [50,56,57]. In spite of this discrepancy, the developed 2D model is still sufficient to capture the main feature of the observed electroosmotic flow patterns in our experiments, which will be presented in Ssection 4.…”

“…This h value is recognized to be much larger than that reported in Ref. [49] and those used in other studies [50,56,57], which indicate that Joule heating of the fluid was dissipated mainly through the bottom glass slide in our microchannel. It is because glass has a much higher thermal conductivity than PDMS [50,56,57].…”

Numerical modeling of Joule heating‐induced temperature gradient focusing in microfluidic channels

“…It is well known that Joule heating results from the inevitable volumetric heating when an electric field is applied across a conducting medium such as an electrolyte. Such heat would lead to an increase in the buffer temperature and develop temperature gradients in the buffer solution along both radial and axial directions of the microchannel [14]. In this study, we will present a numerical Figure 1.…”