Rapid AC Electrokinetic Micromixer with Electrically Conductive Sidewalls

Abstract

We report a quasi T-channel electrokinetics-based micromixer with electrically conductive sidewalls, where the electric field is in the transverse direction of the flow and parallel to the conductivity gradient at the interface between two fluids to be mixed. Mixing results are first compared with another widely studied micromixer configuration, where electrodes are located at the inlet and outlet of the channel with electric field parallel to bulk flow direction but orthogonal to the conductivity gradient at the interface between the two fluids to be mixed. Faster mixing is achieved in the micromixer with conductive sidewalls. Effects of Re numbers, applied AC voltage and frequency, and conductivity ratio of the two fluids to be mixed on mixing results were investigated. The results reveal that the mixing length becomes shorter with low Re number and mixing with increased voltage and decreased frequency. Higher conductivity ratio leads to stronger mixing result. It was also found that, under low conductivity ratio, compared with the case where electrodes are located at the end of the channel, the conductive sidewalls can generate fast mixing at much lower voltage, higher frequency, and lower conductivity ratio. The study of this micromixer could broaden our understanding of electrokinetic phenomena and provide new tools for sample preparation in applications such as organ-on-a-chip where fast mixing is required.

Mixing and Flow Transition in an Optimized Electrokinetic Turbulent Micromixer

“…It should be noted that if the applied AC frequency is over 200 kHz, the voltage amplifier exhibits rapid attenuation and waveform distortion. Besides, some previous investigations have shown that a larger AC frequency, e.g., above MHz, cannot induce apparent mixing enhancement and turbulent flow . Therefore, all of the experiments are conducted at no more than 200 kHz.…”

“…Besides, some previous investigations have shown that a larger AC frequency, e.g., above MHz, cannot induce apparent mixing enhancement and turbulent flow. 53 Therefore, all of the experiments are conducted at no more than 200 kHz.…”

Biochemical Reaction Acceleration by Electrokinetic Mixing in a Microfluidic Chip

“…The results showed that this frequency enabled faster and more thorough mixing of liquid samples, allowing for faster enzymatic catalysis reaction. According to our previous results, the lower the frequency, the better the mixing effect, but when the frequency is too low, bubbles will form in the channel, which will block the channel and reduce the mixing efficiency. In the present study, 500 kHz was the optimal frequency that gave the best mixing result without generating any bubbles.…”

“…Through theoretical and experimental study, we found that voltage, frequency, and conductivity ratio were the key factors that directly affect the μEKT mixing efficiency (Supporting Information: Theory Background). 18 Mixing efficiency could be improved by increasing the voltage and conductivity difference, decreasing the flow rate (Supporting Information Figures S1−S3) and frequency. 18 Therefore, we will study the direct effects of these parameters on the efficiency of biochemical reactions.…”

“…18 Mixing efficiency could be improved by increasing the voltage and conductivity difference, decreasing the flow rate (Supporting Information Figures S1−S3) and frequency. 18 Therefore, we will study the direct effects of these parameters on the efficiency of biochemical reactions.…”