Joule heating and heat transfer in poly(dimethylsiloxane) microfluidic systems

Abstract

Joule heating is a significant problem in electrokinetically driven microfluidic chips, particularly polymeric systems where low thermal conductivities amplify the difficulty in rejecting this internally generated heat. In this work, a combined experimental (using a microscale thermometry technique) and numerical (using a 3D "whole-chip" finite element model) approach is used to examine Joule heating and heat transfer at a microchannel intersection in poly(dimethylsiloxane) (PDMS), and hybrid PDMS/Glass microfluidic systems. In general the numerical predictions and the experimental results agree quite well (typically within ± 3 °C), both showing dramatic temperature gradients at the intersection. At high potential field strengths a nearly five fold increase in the maximum buffer temperature was observed in the PDMS/PDMS chips over the PDMS/Glass systems. The detailed numerical analysis revealed that the vast majority of steady state heat rejection is through lower substrate of the chip, which was significantly impeded in the former case by the lower thermal conductivity PDMS substrate. The observed higher buffer temperature also lead to a number of significant secondary effects including a near doubling of the volume flow rate. Simple guidelines are proposed for improving polymeric chip design and thereby extend the capabilities of these microfluidic systems.

Joule heating effects on electroosmotic flow in insulator‐based dielectrophoresis

“…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].…”

“…The application of electric field induces Joule heating within the fluid, which, however, extends to both the PDMS and the glass substrates through thermal diffusion in all three dimensions [50]. This significantly complicates the thermal modeling.…”

Analytical investigations on the thermal properties of microscale inorganic light-emitting diodes on an orthotropic substrate

“…10,12,15 The specific heat capacity and density of the encapsulation layer (SU8) is 1200J/kg/K and 1090kg/m 3 . 14 Figure 5(a) shows the saturated temperature increase of the µ-ILED from the analytical predictions in Eq.…”