A Technique for Detecting the Presence of Water Under micro-Devices working in a Liquid Environment

This study address issues specifically related to the underwater dynamic actuation of Micro Electro Mechanical Systems (MEMS), such as micro-cantilevers or comb-drive microstructures. As a practical application, cantilevers made using MUMPs (Multi-User MEMS Processes) foundry are considered. Since the gap between the cantilevers and the underlying surface is very narrow (about 2 μm), water does not always flow easily underneath the cantilevers, especially when the surface is hydrophobic with respect to the liquid environment. As long as the MEMS surface is hydrophobic, the lower the gap, the higher the pressure required to flow into micro-channels or gaps . As a consequence, this issue significantly modifies cantilevers’ performances. To gain an insight of the phenomenon, a new measurement technique was developed, referred to as MFTEC (MEMS Freezing by Thermo Electric Cooling), which can verify the presence of water under cantilevers or other micro-devices