A wireless self-powered urinary incontinence sensor embedded in disposable diapers

A self-powered urinary incontinence sensor with a flexible wire-type urine-activated battery that is embedded in a diaper has been developed as an application for wireless biosensor networks. Since the battery is flexible, it conforms to the shape of the diaper when the diaper is worn. The stress produce by the curvature presses the electrodes firmly against the diaper material, providing greater contact with any urine present. Thus, due to the curvature, the battery generates more power than when it is flat, as in an unworn diaper. The battery also acts as a wide ground plane for the antenna of a wireless transmitter, providing a large radiated power. To verify the effectiveness of the battery, we fabricated a battery and a prototype sensor and embedded the battery in a diaper. When 80 cc of urine is poured onto the diaper, the battery outputs a voltage of 1 V, which allows the sensor to transmit an ID signal over a distance of 5 m.