Flexible Strain-Sensitive Silicone-CNT Sensor for Human Motion Detection

This article describes the manufacturing technology of biocompatible flexible strain-sensitive sensor based on Ecoflex silicone and multi-walled carbon nanotubes (MWCNT). The sensor demonstrates resistive behavior. Structural, electrical, and mechanical characteristics are compared. It is shown that laser radiation significantly reduces the resistance of the material. Through laser radiation, electrically conductive networks of MWCNT are formed in a silicone matrix. The developed sensor demonstrates highly sensitive characteristics: gauge factor at 100% elongation −4.9, gauge factor at 90° bending −0.9%/deg, stretchability up to 725%, tensile strength 0.7 MPa, modulus of elasticity at 100% 46 kPa, and the temperature coefficient of resistance in the range of 30–40 °С is −2 × 10−3. There is a linear sensor response (with 1 ms response time) with a low hysteresis of ≤3%. An electronic unit for reading and processing sensor signals based on the ATXMEGA8E5-AU microcontroller has been developed. The unit was set to operate the sensor in the range of electrical resistance 5–150 kOhm. The Bluetooth module made it possible to transfer the received data to a personal computer. Currently, in the field of wearable technologies and health monitoring, a vital need is the development of flexible sensors attached to the human body to track various indicators. By integrating the sensor with the joints of the human hand, effective movement sensing has been demonstrated.

Flexible, Sensitive, Multifunctional Rubber-based Sensor with Multiple Responses to Infrared, Temperature, Humidity and Strain

Flexible wearable electronic sensors have attracted immense interest in human motion detection, body temperature monitoring and personal healthcare monitoring. However, most of reported sensors cannot integrate multifunctional applications at the same time though they own excellent single achievement of strain sensing or humidity sensing. Herein, we fabricate a multifunctional rubber-based flexible sensor (MRFS) with responses to infrared, temperature, humidity and strain. The sensor owns a superior strength (5.66 MPa), high stretchability (367%), high temperature coefficient of resistance (2.046%/℃) and high photothermal conversion efficiency (78.6%). For the sensing applications, it shows a rapid sensing of only 0.5 s for the temperature and humidity changes as well as a sensitive response to low-powered near infrared of 0.14 W/cm2, body temperature change from 33.6 to 35.6 ℃, and small amount of moisture on human skin. Moreover, the MRFS shows a considerable strain sensing for human joint motion and an antibacterial property.