On the Dynamic Stability of Gold Electrodes Exposed to Alternative Voltages in Microfluidic Systems
Qi Wang, Shuren Song, Wei Wang, Jia Zhou +1
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70% confidenceThis study investigates the dynamic stability of gold electrodes in microfluidic systems exposed to alternative voltages, revealing that the dissolution threshold voltage depends on the ratio of reaction to diffusion rate, as quantified by the Damkhöler number. The research explores the effects of voltage amplitude, actuation frequency, pH, and electrolyte composition on gold electrode stability. The findings have implications for the design of microfluidic devices and the use of gold electrodes in various applications, including Microbial Electrochemical Systems (MES).
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Abstract
While gold is a stable metal in water, it is not uncommon for microfluidic experimenters using biologically-relevant fluids such as phosphate-buffered saline (PBS) to witness their precious gold electrodes quickly vanish from the microchannel once the voltage exceeds a few volts. This stability issue concerns multiple fields where high voltage provides superior actuator or sensor performance, such as resistive pulse sensing (RPS), electroosmosis, electrowetting and so on. One solution to protect metallic electrodes is using alternative voltages (AV) as opposed to continuous voltages. After recalling that gold dissolution is enabled by the chloride ions present in most biologically-relevant solutions, we explore the stability conditions of the electrodes for voltages from 1 to 20 V pp (Peak to Peak voltage amplitude), actuation frequencies between 0 and 5 kHz, and for various pH and electrolytes (NaCl, Na 2 SO 4 , HCl). We find that the dissolution threshold voltage depends on the ratio of reaction to diffusion rate given by the Damkhöler number Da. In mass-transfer limited regime, the dissolution threshold is independent of the frequency, whereas the dissolution voltage is observed to grow as Da −1/2 in the reaction limited regime. These findings provide guidelines to design more reliable electrowetting, electroosmosis, dielectrophoresis and resistive pulse sensing devices.
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Identifiers
- Journal
- Journal of The Electrochemical Society
- Year
- 2022