Bubble profile reconstruction with miniaturized sensors in a microchannel

Abstract

The thickness of thin liquid film underneath a bubble in a microchannel is important for the bubble evolution and heat transfer studies. A minimized sensor matrix based on conductance measurements and fabricated with standard photolithography technology was developed to measure the liquid film thickness underneath a gas slug directly and dynamically. This sensor matrix was made up of 5 × 5 electrode pairs and each pair was comprised of a transmitter and a receiver electrode concentrically. The outer diameter of the electrodes is 310 µm. These sensor pairs were distributed on the surface of a wafer, covering a total length of 8 mm and width of 2 mm. Calibrations of the sensor characteristics were performed with known thickness of liquid film in a series of microchannels. Further dynamic measurements were conducted in order to study the bubble profile in micro scale directly and accurately.