Abstract

We report the fabrication and characterization of responsive dielectric metasurfaces composed of titanium dioxide (TiO₂) nanocrystals (NCs) and chitosan hydrogel biopolymer composites. Chitosan is controllably introduced into aqueous TiO₂ NC dispersions to formulate adaptive inks. The inks are then used in a nanoimprinting process to produce moisture-responsive metasurfaces with high quality factor (Q), quasi-guided mode (QGM) resonances. The metasurfaces function as environmental relative humidity (RH) sensors, exhibiting a 250% enhancement in sensitivity with the addition of chitosan─to a maximum of 0.29 nm/%RH. This work presents a scalable, single-step, room-temperature strategy for producing optically tunable metasurfaces in the visible, offering high sensitivity and quality factor resonances, and enabling enhanced optical humidity sensor performance.

https://pubs.acs.org/doi/10.1021/acsanm.5c02711