Joule heating effects on electrokinetic flows with conductivity gradients

Area of Science:

• * Physics and Chemistry of Fluids
• * Microfluidics and Transport Phenomena

Background:

• * Electrokinetic flow instability in microchannels is influenced by fluid conductivity and permittivity gradients.
• * Understanding this instability is crucial for optimizing transport and mixing in microfluidic devices.

Purpose of the Study:

• * To investigate the impact of Joule heating on electrokinetic instabilities in microchannel flows with conductivity gradients.
• * To provide the first combined experimental and numerical study on this phenomenon.

Main Methods:

• * Experimental observation of flow patterns and measurement of critical electric fields.
• * Development and application of a depth-averaged numerical model to simulate flow behavior.
• * Analysis of Joule heating effects under varying conditions.

Main Results:

• * Joule heating was found to increase the critical electric field required for electrokinetic instability onset.
• * The numerical model accurately predicted experimentally observed flow patterns and critical fields.
• * Increased fluid temperature due to Joule heating, leading to decreased permittivity, was identified as the primary mechanism.

Conclusions:

• * Joule heating stabilizes electrokinetic flows by raising the critical electric field.
• * This stabilization effect is attributed to temperature-induced changes in fluid permittivity.
• * The findings offer insights for controlling fluid behavior in microfluidic applications through thermal management.