Skin hydration state estimation using a fiber-optic refractometer

A U-shaped fiber-optic refractometer is used to estimate the hydration state of human skin. The validity of the sensor in this application has been investigated by comparing the sensor output with the conductance of the skin to a high-frequency electrical current of 3.5 MHz, which has been reported to be a good measure of the skin hydration state. Results indicate that there is a relatively close relationship between the optical sensor output and the electrical conductance. A water sorption-desorption test conducted to confirm the above relationship has revealed that the fiber-optic probe can provide a convenient means for estimating the skin hydration state in an easy manner.