Water detection in skin by dual-band photodiodes

Purpose of this study was to develop a simple model for possibilities to detect water in skin by diffuse reflectance spectra. The model is based on comparison of diffuse reflectance spectra when illuminating water sample with LEDs of different wavelengths (1200 nm, and 1450 nm). The illumination LEDs were chosen due to water absorption differences in near-infrared spectral range. For detection, dual-band photodiodeDSD2 by Thorlabs was used. Due to differences of water absorption at different wavelengths in the near-infrared spectral region, this correlation could be used for mapping of water content in skin or, in other words, determine relative moisture level in skin. Simple experimental setup of illuminating LEDs, detecting photodiode, oscilloscope for measuring the signal received by photodiode, and a sample of water in a Petri plate, was used. The signal of the oscilloscope was interpreted as a parameter that describes intensity of light that is initially illuminated by the LEDs and that travels through the water sample. This study shows the basic principles used and first results, as well as gives insight of further work that will be carried out.