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

Abstract

AbstractAgarose 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.