A Capacitive Sensor that Detects Urination Time and Urine Absorption Volume in Multiple Urinations before Changing a Diaper

Diapers are used by elderly people who require nursing and have difficulty in urinating in the toilet. Some sensors have been developed that detect urination in a diaper. However, most of them cannot evaluate the urine absorption volume. Moreover, if elderly people urinate more than once before a diaper change, the second and subsequent urinations cannot be detected by the developed sensors. Therefore, a capacitive sensor system that can quantitatively evaluate the urine absorption volume multiple times by attaching the sensor to the outer surface of a diaper is developed. In this study, a phantom, i.e., a waist-type torso mannequin, filled with saline solution was used. When pseudo-urine was infused into the diaper, the capacitance rapidly decreased. Afterward, as the absorbed pseudo-urine spread on the diaper, the capacitance drifted and decreased. Furthermore, when the same amount of pseudo-urine was additionally infused into the diaper, the rapid decrease in capacitance became larger. To compensate for the decrease in capacitance, the time from the first urination was employed as a variable. As a result, the compensated values of capacitance change increased linearly with the amount of urine absorption volume in multiple urinations before changing a diaper. An elderly female who required nursing and used diapers participated in this study. In the feasibility test, multiple urinations were quantitatively evaluated.