Electrolytic bubble-based flow sensing using electrochemical resistance measurement in a microchannel

This paper presents a novel method for measuring flow rates in microchannels based on electrolytic bubble generation and electrochemical resistance measurement. The method exploits the generation of gas bubbles by electrolysis of ionic fluid at the surface of electrodes positioned within the microchannel. The flow rate is quantified by measuring the electrical resistance of the electrolyte using electrodes in inter-digitated form. By analysing the bubble frequency and size, the variation in the resistance is investigated and as a result the flow rate can be determined with high accuracy and precision. The proposed method is suitable for a wide range of flow rates, and can be easily integrated into microfluidic systems. We demonstrate the feasibility and performance of the method through experiments using 0.1M NaCl over a range of flow rates in a microchannel with different geometries. Flow measurements are made in range 0–200 μl/min with a measurement sensitivity of 3.17 \(\Omega \) $\mathrm{\Omega }$ /(μL/min) and RSD < 15%. 3 \(\sigma \) $\sigma$ resolution of the sensor is 12.5 μL/min. The rise in fluid temperature is observed to be less than 5 °C at all times. The proposed method has potential applications for on-chip detection in chemical synthesis, drug development and biomedical devices and is easy to implement and scalable.