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

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 “pluglike”
profile. The numerical simulations show that Joule heating not only accelerates
the sample transport but also distorts the shape of the sample band.