Electrolytic-Bubble-Based Flow Sensor for Microfluidic Systems

Accurate measurement and control of flow properties are essential for microfluidic lab-chips. In this paper, we demonstrate an electrolytic-bubble-based approach to directly measure flow rate in microfluidic arteries. By simultaneously generating two gas bubbles electrochemically along a channel, we can measure the pressure difference (and thus flow rate) in real time. A prototype chip that measures flow rate was fabricated on silicon. The sensor was characterized for a functional microfluidic system with inlet pressure ranging from 108 to 135 kPa. The flow-meter performance was compared with computational fluid dynamics simulations and was also calibrated against other direct experiments. The impedance-based flow-rate measurements are easily achieved on a chip with a simple electronic circuit. The described approach can be integrated into any fluid circuit, particularly microfluidic channels that are too small to use off-shelf flow meters.