Nanoclay-based hydrogel for packaging of optical resonator sensors

Optical Whispering Gallery Mode (WGM) microresonators have shown great promise in sensing applications. Various efforts have been made to package WGM sensors in order to enhance their robustness for field applications. Previously, polydimethylsiloxane (PDMS) and other low index polymers have been employed for packaging of WGM sensors. However, the long curing time of PDMS and the rigidity of polymers pose other difficulties, thereby limiting their performance. Hydrogels, with shorter polymerization time and increased flexibility, transparency and biocompatibility, offer a great alternative to current packaging materials. The flexibility and optical transparency of hydrogels, in conjunction with the capability to functionalize them for specific applications, provide superior functionality and improved stability of WGM sensors. Herein we propose the use of laponite nanoclay and N, N, dimethylacrylamide (DMAA) based hydrogel for the packaging of WGM sensors. Microbubble resonators were used for the demonstration of hydrogel-based packaging. The hydrogel was synthesized by mixing DMAA in exfoliated nanoclay suspension at different concentrations with sodium persulfate as an initiator and Tetramethylethylenediamine (TEMED) as an accelerator. The microbubble resonators were packaged on 3D-printed chips and were characterized through their transmission spectra.