Design of Textile Capacitive Pressure Sensor

Pressure significantly influences both our external interactions and internal bodily functions. With the global population aging, there has been a heightened focus on healthcare monitoring devices, essential for enhancing longevity and quality of life. These devices are crucial for early disease detection, real-time monitoring of treatment effects, and general health tracking, leading to a surge of interest in wearable electronics. Such wearables can seamlessly integrate with the human body to monitor various health indicators like heart rate, blood pressure, and motion.<br/>Traditional rigid and heavy pressure sensors have evolved into flexible, lightweight, and adaptable versions suitable for wearing on the human body. This innovation has resulted in sensors with excellent resolution and rapid response times, making them practical for modern applications.<br/>Despite advancements, challenges persist in the manufacturing processes of soft pressure sensors. Researchers have recently focused on textiles for wearable electronic applications due to their softness, breathability, and flexibility. Textiles offer unique benefits, such as sensing strain, pressure, and temperature. Their three-dimensional porous structure can enhance device performance by introducing air gaps. Additionally, textiles are cost-effective and easy to produce on a large scale, making them a promising material for wearable pressure sensors.<br/>Textile flexible pressure sensors hold significant potential in various fields, including wearable electronics, soft robotics, human-machine interfaces, sports, biomedical devices, and human motion analysis. However, typical textile-based pressure sensors often suffer from limited sensitivity and a narrow working range because they use extra chemical material as a dielectric between the fabric layers. These sensors also have limitations, such as not being washable, not being suitable for application on the skin, and losing their properties under high pressure.<br/>In contrast, the unique structure of cut pile fabric, when left uncovered by any other material, can trap air and serve as a dielectric. This allows for better pressure distribution and an increased contact area, leading to improved sensitivity and resolution. Additionally, the flexibility and structure of the cut pile enable rapid response times, and the absence of extra material maintains the sensors' lightweight, breathable, and washable nature.<br/>Herein, we present wearable capacitive pressure sensors fabricated entirely from cut-pile fabrics. Cut-pile fabrics consist of a knitted framework with cut piles looped through at regular intervals. We describe the selective metallization of the framework to provide the electrodes and use the cut piles as the dielectric medium. The cut piles provide a structure that effectively traps air between the cut pile fibers, which is integral to the sensor's functionality and performance, enhancing sensitivity, flexibility, breathability, mechanical response, and comfort. This makes it particularly suitable for various applications, especially in wearables.<br/>We discuss the characterization of these new textile sensors and demonstrate their effectiveness across three different pressure ranges (0-10 kPa), (10-30 kPa), and (30-500 kPa).<br/><br/><b>References:</b><br/>Chen, Wufan, and Xin Yan. "Progress in achieving high-performance piezoresistive and capacitive flexible pressure sensors: A review." Journal of Materials Science & Technology 43 (2020): 175-188.<br/>Su, Min, Pei Li, Xueqin Liu, Dapeng Wei, and Jun Yang. "Textile-based flexible capacitive pressure sensors: A review." Nanomaterials 12, no. 9 (2022): 1495.<br/>Pignanelli, Julia, Kory Schlingman, Tricia Breen Carmichael, Simon Rondeau-Gagné, and Mohammed Jalal Ahamed. "A comparative analysis of capacitive-based flexible PDMS pressure sensors." Sensors and Actuators A: Physical 285 (2019): 427-436.