Nanofabrication of polymer micro-ring resonator on a soft substrate as a flexible ultrasonic detector (Conference Presentation)

Flexible ultrasonic detectors can hold promise for continuous real-time, long-term, and high-quality photoacoustic (PA) imaging by conformal contact to samples with non-planar surfaces. Polymer micro-ring resonators (MRRs) have been proven to be one of the most versatile choices for ultrasonic detections, due to their high detection sensitivity over a wide frequency range, optical transparency, and at a significantly miniaturized form-factor. However, polymer MRR ultrasound detectors being reported were all fabricated on rigid substrates. To address this issue, here we report the development of a new process for nanofabricating MRRs on soft polymer substrate. We optimized the nano-fabrication process to better accommodate the added compliance of the soft polymer substrate, while retaining the low-cost nature of the nano-imprinting process. The choice of the materials has also been optimized. Finally, we validate the characteristic performance of the fabricated flexible MRR ultrasound detectors experimentally.