ABSTRACT
A novel highly sensitive cone structured porous polydimethylsiloxane (PDMS) based pressure sensor capable of detecting very low-pressure ranges was developed for wearable respiration monitoring applications. The pressure sensor was fabricated using a master mold, a dielectric layer and fabric-based electrodes. The master mold with inverted cone structures was created using a rapid and precise three-dimensional (3D) printing technique. The dielectric layer with a porous and cone structures was prepared by annealing the mixture of PDMS, nitric acid (HNO3) and sodium bicarbonate (NaHCO3) in a master mold with inverted cone structures. The electrodes were developed by screen printing silver on fabric. A sensitivity of approximate to 530 %kPa(-1) was measured for the fabricated pressure sensor at ultra-low-pressure ranges from 0 Pa to 10 Pa. The porous-cone structures provided an excellent deformation and thus resulted in high sensitivity for detecting very low pressure ranges below 100 Pa (135 %kPa(-1)). As application demonstration, the pressure sensor was sewed inside a surgical mask and it's capability to detect different respiration rates (normal, fast, and deep breathes) was investigated. An airflow controller system and custom-built software was also developed for performing the continuous sensor data acquisition and capacitance conversions while changing the airflow rate.