Investigation of SU-8 as protection layer for prism SPR sensor towards reusable honey adulteration detection

This study presents the development of an Ag-based SPR sensor with the presence of SU-8 photoresist film as a protection layer for honey adulteration detection. The pure honey was adulterated by heating process from 30% until 18% water content of adulterated honey. The performance of Cr-Ag-(SU-8) SPR sensor was compared with the Cr-Ag SPR sensor without a protective layer. The resonance angle for these two sensors indicates a similar behavior by shifting to a higher angle than the pure honey. The sensor sensitivity for Cr-Ag and Cr-Ag-(SU-8) is 0.24448°/% which produces a linear regression of more than 96% for honey samples. The resonance angle for Cr-Ag-(SU-8) SPR sensor shows the same values after 24 hours although the reflectance curve is slightly broader. This proved that the SU-8 is capable to protect the Ag surface for repeatable uses. This work is a preliminary study of SU-8 for SPR protection layer to detect the adulteration of honey which based on the percentage of water content.