Advances in miniaturized biomedical microsystems, ranging from in vitro microphysiological systems (MPS) to implantable devices, are enabling new modes of continuous, autonomous preclinical studies. This thesis presents a set of interconnected research contributions on millimeter-scale fluorescence-sensing and ultrasonic energy-harvesting microsystems, collectively advancing the development of integrated and miniaturized biomedical instrumentation. The first part introduces an integrated microoptical system for fluorescence sensing in MPS, incorporating custom micro-optics and miniaturized excitation and detection units with tailored optical filters. This platform enables real-time, continuous fluorescence monitoring of microtissues under physiologically relevant conditions, strengthening the analytical capabilities of MPS for long-duration studies of drug delivery and cellular behavior. The second part translates these sensing concepts to fully implantable microsystems capable of autonomous, long-term in vivo fluorescence recording. A compact 5 × 5 × 5 mm³ implant integrates a miniaturized optical module and low-power electronics to track fluorescence dynamics within living tissue. Validated across phantom, in vitro, ex vivo, and in vivo studies, the system demonstrates two-week continuous tracking of tumor-associated fluorescence, establishing its suitability for preclinical studies. The final part focuses on ultrasonic energy harvesting to enable the autonomous operation of implantable devices. A MEMS-based piezoelectric ultrasonic energy harvester (PUEH) fabricated using a low-temperature bonding process allows integration of high-performance bulk PZT-5H, demonstrating the potential of MEMS architectures for efficient ultrasonic power transfer. An integrated energy-harvesting node, also in a 5 × 5 × 5 mm³ form factor, combines the MEMS-based PUEH with power management and storage to support autonomous operation of millimetric implants. Together, these contributions advance miniaturized fluorescence sensing and ultrasonic energy transfer, enabling versatile microsystems for biomedical applications.
Xu Tian (Thu,) studied this question.