Selective deposition of chemically-bonded gold electrodes onto PDMS microchannel side walls

• Gold electrodes were chemically-bonded on vertical side walls of a microchannel.
• Simulations showed the impact of electrode configuration on the electric field.
• Side wall electrodes yield a uniform electric field, ideal for many applications.
• Surface modification was confirmed by ATR-FTIR and gold deposition by SEM/EDX.
• Electrodes were electrochemically stable and resistant to shear.

Many applications of microfluidic devices require the incorporation of electrodes. In this paper, we describe the simulation, fabrication, and performance of gold electrodes selectively deposited on the side walls of a microchannel. Electrode microfabrication methods typically pattern metal electrodes onto a flat substrate. However, when anode and cathode are both positioned on the bottom of a microfluidic channel, the electric field is not uniform with channel depth. Finite element modeling was used to characterize field distortion for conventional electrode placement vs. side wall positioning for a range of microchannel geometries. These models showed that electrodes located on microchannel side walls created an electric field that was uniform with depth at all points within the channel, while electrodes deposited on the bottom substrate resulted in a 10–40% decrease in potential vertically along the microchannel side wall. This paper also demonstrates a new fabrication method to chemically bonded gold electrodes along opposing vertical side walls in a closed PDMS microchannel. Deposition of gold on the PDMS microchannel side walls was confirmed by SEM/EDX imaging and electrochemical analysis. Fabricated electrodes were electrochemically stable and resistant to shear.

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