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New Models for Microfluidics

cell culture chamber
Figure 1: Cell
culture chamber

electrical potential  distribution
Figure 2: Electrical
potential distribution

Joule heating image
Figure 3:
Temperature distribution

This article highlights the addition of new modeling capabilities for modeling Joule heating and electrothermal effects in the next release of FLOW-3D.

Even though electrokinetic efforts, such as electroosmosis, can be efficiently used in various micro-fluidic-systems, a drawback is the internal heat generation (commonly referred to as Joule heating). Joule heating is caused by electric currents in the buffer solution. Heat generation makes it difficult to maintain the uniform and controlled buffer temperatures that are important for minimizing dispersion during temperature sensitive chemical reactions such as DNA hybridization. Furthermore, temperature gradients created by a nonuniform electric fields (and thus the power density) result in gradients of fluid conductivity and permittivity. The former produces a free volume charge and Coulomb force, while the latter creates a dielectric force. These two forces cause the medium to flow and are called the electrothermal effects. Generally, the ability to dissipate the heat generated by electric, current is what limits the strength of the applied electric field and thus the maximum achievable flow rate.

Understanding both Joule heating and electrothermal effects is critical for the proper design of microdevices. In the next release of FLOW-3D, users will have a robust tool to simulate these physical processes. The figures below show the geometry of a cell culture chamber and images from a FLOW-3D simulation. This simulation includes Joule heating, electrothermal effects, and particle dielectrophoresis.