INTRODUCTION
MEMS resonant strain sensors based on vacuum packaged silicon resonators operating in closed loop can produce very high resolution strain measurements up to resolution limits below 1 nε [1]-[5], several orders of magnitude below the performance limits of commercial strain sensors based on metal or semiconductor resistive gauges. However, in resonant MEMS sensors, these very interesting performances are balanced by problems related to the attachment of the sensor on the material under measurement, which is necessary for strain sensing.