A Portable Dual-Parameter Tester for Assessing Electrical Properties of Human Skin Surface

A portable tester for accessing human skin status quantitatively at home is reported. An interdigital electrode (IDE) that contacts directly with human skin is used as the sensing element. The electrode-skin model is simplified as a resistance and a capacitance in series. Using square wave signal for excitation, impedance of the IDE is measured in a charging/discharging way. During one measurement cycle, the response voltages at two excitation frequencies, i.e., 10 kHz and 600 Hz, are measured successively. Equivalent resistance and capacitance of skin are then resolved from the measured values. Both the numerical and experimental simulation results indicate that the proposed circuit and corresponding algorithms work well for resistors and capacitors. The performance of the tester is experimentally tested with human skin in cases of different status. Obvious relationship between the measured values and the skin status is observed. Moreover, distinctive results are obtained between hydrating and emollient cosmetics smeared skins. The tester can be potentially used to give a quantitative guidance for individual skin care, such as cosmetics selection.