3D textile structure-induced local strain for a highly amplified piezoresistive performance of carbonized cellulose fabric based pressure sensor for human healthcare monitoring

Environmental issues have led to increasing interest in the use of biomass materials to make wearable sensors; cellulose is an environmentally-friendly material that has attracted particularly substantial attention. This study is the first to achieve amplified piezoresistive properties by applying a 3D textile structure to a sensor made of carbonized cellulose fabric (CCF). By using the pre-strained monofilament of 3D textile as a pressure transmitter, the local strain in the CCF can be increased to enlarge the contact area between the CCF fibers, which in turn improves the sensitivity by 9.6 times (32.13 kPa(-1)) at the same pressure (3.35 kPa(-1)). The results showed that large joint motions (finger and knee joint motion, gait) and bio-signals (wrist pulse, speaking, breathing, etc.) could be monitored in real time with excellent sensitivity. Further, different neck movements occurring in four directions could be detected through a 4-way sensor that utilizes compression behavior, which varies based on the difference in monofilament length and density of the four different 3D textiles. All collected information can be transmitted to the user's smartphone through the Bluetooth module, which indicates that the sensor is suitable for implementations in healthcare monitoring. The proposed sensor can both enable novel applications of 3D textiles as well as provide a convenient and cost-effective approach.