Vibrational MEMS for Mass Detection and Energy Conversion

The presented thesis summary highlights the most important points of the research work about the development of Micro-Electro-Mechanical-Systems (MEMS) aimed to the quantitative mass detection, to the energy conversion from electrical to chemical. First of all, a torsional microbalance for mass detection, and specifically for applications in the medical field for genetic diseases diagnosis, will be presented. Specifically, starting from the mathematical analysis of the device and from FEM simulations, a MEMS able to output an electrical signal proportional to the quantity of mass that is adsorbed on the device has been designed, fabricated, characterized and optimized. The principal advantages of the device rely on the fact that both the actuation and the transduction mechanisms are electromagnetic, avoiding the undesirable thermal drift spurious effects as in the case of the mass sensors based on piezoelectric sensing and sticking issues as in the case of mass sensors based on capacitive sensing. Certainly, the most important advantage rely on the fact that the sensor is fabricated in a CMOS-compatible technology (BCD6 by STMicroelectronics), even allowing, as shown in the thesis, the possibility of implementing the readout and conditioning electronics on board. Further, in the field of MEMS based on mechanical excitation of the micro-machined resonating structure, a device for energy conversion will be presented. It is a macroscopic prototype, but with characteristics that make miniaturization possible, of a micro-droplet fuel ejector, based on a novel technique developed by the US research team of the Cornell University, for energy conversion from electrical to chemical. It has been demonstrated that it is possible to get 600mW as output power compared to the 60mW used for the driving electronic system with a total efficiency of 2%.