PhD defence of Roufaida Bensalem – Innovative Designs and Implementations of Capacitive Micromachined-Based Solutions for Sensing and Actuation
Abstract
This Ph.D. thesis focuses on micromachined ultrasonic transducers (MUTs) for sensing and actuation, emphasizing capacitive micromachined-based devices. The research encompasses developing and characterizing innovative MEMS-based solutions, addressing various challenges in the field.
One significant contribution of this work is the development of a micro-viscometer that uses a capacitive micromachined ultrasonic transducer (CMUT) and a low-power transceiver ASIC. The system can monitor engine oil viscosity, detect technical defects early on, and provide insights into the engine's condition, leading to optimally timed oil change intervals. MUTs in this application offer a low-cost and small-size solution for engine oil monitoring.
Another significant contribution is the development of a repulsive actuation-based MEMS varactor that exhibits an ultra-linear capacitance-to-voltage response. This approach achieves high linearity in the capacitance-versus-voltage response, without any abrupt capacitance change or pull-in voltage limitation. The potential applications of this development include VCOs, PLL circuits, and various electrical circuits to achieve low phase noise and large capacitance tuning ratios.
Lastly, the research investigates a novel approach to enhance ultrasound transmission using capacitive micromachined ultrasonic transducers (CMUTs). The CMUT design proposed achieves increased cavity height and out-of-plane displacement through electrostatic repulsion. Simulation results demonstrate a notable improvement in the range of motion and enhanced sound pressure transmission. Experimental tests validate the effectiveness of the proposed approach, showcasing substantial improvements in ultrasound transmission over a wide frequency band. This research opens doors for applications such as ranging, gesture recognition, and non-destructive testing.
Overall, this Ph.D. thesis advances micromachined ultrasonic transducers, particularly capacitive micromachined-based devices, for sensing and actuation. The research provides valuable insights that can further improve MUT design and implementation, resulting in more efficient, cost-effective, and sustainable solutions.