Development of a sensor with a conductive textile for detecting decubitus ulcers

The present paper describes the design and evaluation results of a sensor for measuring body pressure and sweat volume using conductive fibers. Pressure ulcers that develop from staying in the same posture for a long time are a serious problem in nursing care. The main causes of pressure ulcers are blockage of capillaries due to body pressure and skin structure degeneration due to sweat. To quantify the causes of pressure ulcers, Mengeng Liu et al. have developed a sensitive (14.4 kPa −1 ) pressure sensor using conductive fibers with excellent cleaning and flexibility. However, a conductive fiber sensor that focuses on both body pressure and sweating has not yet been established. Therefore, in the present research, we made a sensor that can measure body pressure and sweat volume with only fibers and evaluated the performance of the proposed method. The fabricated sensor is a parallel plate capacitive sensor made of two conductive fibers that sandwich an insulating cloth. When body pressure is applied, the distance between two parallel conductive fibers increases, and when sweat is applied, the dielectric constant of the fabric changes, increasing the capacitance of the sensor. Capacitance change can be evaluated by peak holding the output of the AC bridge circuit. Through an evaluation experiment using a vise and a constant temperature and constant‐humidity chamber, the fabricated sensor was confirmed to be able to measure a pressure change of 10 mmHg and a humidity change of 10%. This sensor, which can evaluate pressure and humidity (amount of adhering water) at the same time and at low cost, contributes to reducing the burden of nursing care. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.