Fluid mixing using AC electrothermal flow on meandering electrodes in a microchannel

Area of Science:

• Microfluidics
• Electrokinetics
• Biochemical Analysis

Background:

• Efficient fluid mixing is crucial for microfluidic applications.
• Conventional mixing methods often face limitations in microscale environments.
• AC electrothermal flow (AC-ETF) offers a potential solution for enhanced mixing.

Purpose of the Study:

• To develop and evaluate a novel microfluidic mixer utilizing AC electrothermal flow (AC-ETF).
• To investigate the influence of salt concentration and AC frequency on mixing performance.
• To demonstrate the mixer's capability for biochemical analysis, specifically protein labeling.

Main Methods:

• Fabrication of a microchannel with coplanar electrodes featuring a sinusoidal interelectrode gap.
• Performance evaluation using dilution experiments with Texas Red-labeled dextran.
• Investigation of mixing efficiency across varying salt concentrations (10⁻³ to 10⁻¹ mol dm⁻³) and AC frequencies (100 kHz to 5 MHz).
• Assessment of the mixer's utility in a fluorogenic reaction involving human serum albumin (HSA) and SYPRO Red.

Main Results:

• AC-ETF effectively enhanced mixing at salt concentrations above 10⁻² mol dm⁻³.
• At lower concentrations (<10⁻² mol dm⁻³) and low frequencies, AC electroosmotic flow (AC-EOF) was suggested to contribute to mixing.
• The mixer demonstrated significant enrichment of fluorescence intensity and uniform distribution of stained HSA.
• Mixing efficiency was found to be dependent on both salt concentration and applied AC frequency.

Conclusions:

• The developed microfluidic mixer utilizing AC-ETF provides an efficient method for fluid mixing.
• The device is suitable for various chemical and biomedical analyses requiring precise fluid manipulation.
• The sinusoidal electrode design enhances mixing performance within microfluidic devices.
• This technology holds promise for advancing microfluidic-based analytical systems.