An integrated electronic meniscus sensor for measurement of evaporative flow

This paper presents an electronic sensor for evaporative flow measurements in open microfluidics Lab-on-Chips. The flow counteracts the gravitational fall of cells in the culture media. Particular attention has been paid in the design to allow the integration of the sensor in biochips composed of large arrays of microfluidic channels for parallel bioassays. Simple Aluminium electrodes produced with a biocompatible technology are used for impedance measurements of the meniscus height h at the outlet of a microchannel. The correlation between the electrical measurement and h is demonstrated with a resolution of 10μm. A second correlation between h and the evaporation rate ER is investigated through optical inspection at different temperatures. Experiments show that the flow rates produced and measured in the device range from 0.16 to 0.32 ul/h at room temperature and 35% relative humidity.