RELIABILITY TESTING AND IMPROVEMENT OF POLYMER HINGE-BASED MEMS SCANNING MIRRORS

Ultrasound and photoacoustic imaging techniques can benefit greatly combined with MEMS scanning mirror technology. Such mirrors can be designed with small enough form factors to fit into handheld imaging probes and the study presented in this thesis goes into (1) analyzing the performance of such a single-axis scanning mirror, (2) improving its design to function more robustly at higher scanning angles, (3) allow for precise monitoring and control of the angle using magnetic sensor. The scanning mirror consists of an aluminum deposited silicon mirror plate on top of a laser-cut flexible polymer double hinge structure and two permanent magnets, which allow for single-axis movement through electromagnetic actuation. This mirror’s operation was tested to verify its reliability. Through the tests, it was determined that the device could reliably operate at ±3° scanning angles without any degradation in performance, but at ±6° showed a steady decline in performance. Following these results, the mirror design was modified by doubling the length of the polymer hinges to generate twice the scanning angle. The redesigned mirror’s operation was tested ±6° scanning angle and proven to no longer go through performance degradation. The resonant frequency under water of the new mirror was also boosted by replacing the rectangular mirror plate with an elliptical one, fabricated using reactive ion etch. A linear-Hall effect sensor was also later added to the device and calibrated accordingly to allow for more precise monitoring of the scanning angle and hence, further improve the reliability of our final mirror device package