Effect of agarose concentration on coated micro‐bottle resonators for humidity detection

Abstract

Agarose is a stable hydrophilic material commonly used for relative humidity sensing application. Agarose porous nature causes changes in its refractive index as relative humidity change. Micro bottle resonators are a promising choice for sensing applications due to their good quality factor. In this work, the effect of agarose gel concentration on micro-bottle ability to detect relative humidity changes was investigated. The agarose gel coating was made in two different concentrations 0.5% and 1%. These two concentrations were used as coating for microbottle resonators with the diameter of 190 μm. The micro-bottle samples were made by the soften-and-compress technique. In the humidity range of 35%-85% RH, the 0.5% agarose gel coated microbottle had a sensitivity of 0.1077 dB/RH%. The microbottle resonator coated with the 1% solution showed a lower sensitivity of 0.0899 dB/ RH%. This improvement in sensitivity with lower agarose gel concentration is due to the pore size of agarose gel. Yet, both concentrations showed improvement in sensitivity compared to the bare micro-bottle showing that agarose can be a potential choice for building sensitive efficient relative humidity sensors.

Review of Microbottle Resonators for Sensing Applications

“…The agarose gel was a 0.5% solution. In addition, 1% agarose gel was used to coat a similar MBR structure, which showed a sensitivity of 0.0899 dB/RH% [52,53]. HEC/PVDF-coated MBR had a 0.111 dB/RH% sensitivity in the 40-80%RH relative humidity range [54].…”