Liwei Lin (Advisor)

This work introduces contactless ultrasonic fluid viscosity and density monitoring using piezoelectric micromachined ultrasonic transducers (pMUTs) for the first time. Key advancements include: (1) non-contact and simultaneous liquid viscosity and density measurements; (2) 98% classification accuracy for four tested liquids; and (3) a mean absolute error (MAE) of 0.79 cp for a viscosity range from 0.98 cp to 39.44 cp, and a MAE of 12.6 kg·m⁻³ for a density range from 997.8 to 1035.3 kg·m⁻³. By removing the requirement for the direct contract of MEMS sensors to the testing fluid, this...

This work presents an alignment-free blood vessel monitoring microsystem based on a piezoelectric micromachined ultrasonic transducer (pMUT) array using a beam steering scheme. Compared with the literature, three key achievements include: (1) quantifications for the impact of misalignments during the ultrasound detection of a brachial artery; (2) a beam steering strategy without manual alignment to expand the field of view; (3) a new technique based on the fast Fourier transform (FFT) phase shift to measure relative location changes of the anterior and posterior artery wall. Validations on...

Advanced design for weakly coupled resonators (WCRs) based on micro disk-shaped structures has been developed using an automatic active optimization (AAO) process with low coupling factors. Previous design methodologies have often used supervised learning (SL) with genetic algorithm for the optimization process but the limited initial design domain in the SL-based predictor often results in local instead of global optimizations. This AAO scheme can generate superior designs in the neighborhood of initial high-density dataset regions and add newly-found designs to the original dataset to...