Continuously Monitoring Healthcare Systems Using Negatively Responsive Switching Conductive Fiber-Based Strain Sensor for Nearly Zero Standby Power

One of the primary challenges in the field of e-textile-based healthcare monitoring systems, particularly for patients with chronic illnesses, is the reduction of wasted power consumption. Conventional healthcare systems need to be always active to capture a broad spectrum of biochemical and physiological characteristics. In particular, wearable monitoring system based on conductive fibers exhibit a positive gauge factor (GF); the electrical resistance of conductive fibers was increased when they are stretched, so that the monitoring system consume the electrical power continuously. Herein, we developed an innovative solution; a twisted conductive fiber-based negatively responsive switch-type (NRS) strain sensor that exhibited high negative GF ~ 3.9 × 10⁸, the conductivity changes from insulated to conductive state. The conductive fiber was coated by the encapsulation layer for induce a difference Young’s modulus between the fiber and encapsulated layer through selective ultraviolet (UV)-irradiation treatment. This UV-induced modification allows the NRS fiber strain sensors to regulate mutual contact resistance effectively under tensile strain. Moreover, these sensors exhibit superior durability, capable of withstanding over 5,000 stretching cycles without performance degradation. The strain sensitivity of these sensors can also be tailored, ranging from 8% to 28% tensile strain, depending on the number of fiber twists. This adjustability makes them versatile for application across various body parts, enabling the detection of different physiological and biochemical conditions. For applications, two specific healthcare monitoring systems using these NRS fiber strain sensors were developed as smart mask and posture correction T-shirts. The smart masks can monitor respiratory patterns and other facial movements, while the posture correction T-shirts can detect and correct improper postures, thus providing comprehensive health monitoring solutions. The developed NRS strain sensor demonstrates a significant step forward in e-textile-based healthcare monitoring systems with near-zero standby power. This work holds promise for enhancing the quality of life for patients with chronic illnesses by providing continuous, reliable, and low-power health monitoring.