Self-powered humidity sensor using chitosan-based plasmonic metal-hydrogel-metal filters

Abstract

We introduced tunable Fabry-Perot resonator using metal-insulator-metal multilayer, in which the insulator is hydrogel foam of chitosan [1]. The chitosan, one of polysaccharide, is responsive to external humidity, so the thickness and refractive index of chitosan change in response to relative humidity (RH); this trait can be utilized to tune resonance wavelegths of the resonator. This tunable color filter can function as humidity sensor when incorporated with photovoltaic (PV) cell. The PV cell transmit input optical spectrum to output current, which enables to determine the relationship between RH h and Response S defined the change in current before and after injection of humidity: S = -0.00002*h^2+0.0046*h-0.0238. Therefore, the response may correctly indicate RH of ambient in real-time. The proposed sensor would be simple to fabricate and potentially have zero-power consumption due to combination with PV cell, which makes the sensor useful for monitoring RH in enclosed spaces, workplaces and storage areas.