Signal Improvement on Fibre Optic Evanescent Wave Sensor Based Polymeric Sensitive Coating of Chitosan-Agarose Hydrogel

This study aimed to explore the correlation between mechanical and structural properties of chitosan (CH) and agarose (AG) hydrogel as a sensitive coating for single-mode optical fibre (SMF) sensors. CH hydrogel was first made without crosslinking as a stock solution at 0.25% w/v concentration before introducing it to AG as the matrix in the fabrication of hybrid-hydrogel (HH). CH was introduced to AG solution in ratio of 1, 2, 5 and 10% w/v concentration to 2% w/v of AG. The highest thickness was shown by a sample of 2% w/v CH to AG hydrogel with an increment of 2.21% from the bare exposed SMF. From the absorption signal measurement, the correlation can be seen as the signal obtained increases directly proportional to the thickness coating. The sensor generated significant signal improvement when HH used a sensitive coating with a refractive index (RI) sensitivity of 3658 ± 0.23352 RIU−1 for glycerol detection.