Humidity Responsive Photonic Sensor based on a Carboxymethyl Cellulose Mechanical Actuator

We describe an intuitive and simple method for exploiting humidity-driven volume changes in carboxymethyl cellulose (CMC) to fabricate a humidity responsive actuator on a glass fiber substrate. We optimize this platform to generate a photonic-based humidity sensor where CMC coated on a fiber optic containing a fiber Bragg grating (FBG) actuates a mechanical strain in response to humidity changes. The humidity-driven mechanical deformation of the FBG results in a large linear change in Bragg resonance wavelength over the humidity range of 5 %RH (relative humidity) to 40 %RH. The measurement uncertainty over this range is ± 2 %RH.