Development of Capacitive Sensor for Diaper Absorption Volume

The number of people requiring care in Japan has increased with the increase in number of people aged 65 or more. Thus, the production of disposable diapers for the elderly is also increasing. Two types of diapers; pad-type and tape-type, are generally used in combination in nursing homes. Diaper change is a burden for both the caregiver and the care receiver. To reduce the number of diaper changes, this study aimed to develops electrodes as a capacitive sensor attached to the outer surface of the tape-type diaper. The capacitive sensor evaluates the absorption volume of the pad-type diaper, and consists of electrodes and a converter circuit that converts the capacitance of electrodes into an output voltage. The study used a waist-type torso mannequin wearing a pad-type diaper on the inside and a tape-type diaper on the outside. The inside of the torso was filled with saline, and the weight of the torso including the saline was 8.9 kg in total. The electrodes were made of copper tape fixed to an insulating film, and the copper tape was 500-mm long and 25-mm wide with a 20-mm interelectrode gap. The electrodes were attached to the outside of the tape-type diaper and connected to the circuit. Experiment was conducted with the torso placed in supine and 30º lateral positions. Tap water (100 mL) was introduced via a silicone tube between the pad-type diaper and the torso hip surface at a flow rate of 7.8 mL / s, which is the average urinary flow rate for the elderly. This procedure was repeated six times. The ex periment was repeated three times. The output voltage increased linearly with increasing volume of water absorbed by the pad-type diaper, in both torso positions. Therefore, the absorption volume was quantitatively evaluated, and the results suggested that the resolution was at least 100 mL when using this sensor.