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

Natalia A Demidenko,Ekaterina Diachkova,Victoria A Zaborova,Artem V Kuksin,Alexander Yu Gerasimenko,Evgeny S Pyankov,Svetlana A Tkachenko,Alexandr A Tsymbal,Hassan Shafaei,Levan P Ichkitidze,Victoria V Molodykh

doi:10.3390/bioengineering9010036

Abstract

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 °C 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.

Highlights

Flexible strain sensors are in high demand in many areas of technology, such as biomedicine and healthcare machines [6], soft robotics [7], interactive games [8], and virtual reality [9], as well as various industrial applications
The developed strain sensors consisted of material that is sensitive to deformations and a portable compact electronic unit for signal reading and processing
The strain sensors consist of a strain-sensitive material, which is a flexible composite consisting of a biocompatible silicone elastomer and carbon nanotubes, equipped with electrodes (Figure 4a) and an electronic unit (Figure 4b)

Summary

Introduction

Bioengineering 2022, 9, 36 for transistors [11], etc.). Existing types of strain sensors, such as fiber Bragg grating (FBG) [13], triboelectric [14], and piezoelectric [15] strain sensors, usually cannot take slow or static deformation due to fast charge transfer. Their practical implementation as wearable devices on the skin remains difficult due to the sophisticated measurement equipment required. Resistive [16] and capacitive [17] sensors require simpler measuring equipment and demonstrate high flexibility and stretchability. Sensors of capacitive and resistive types, in which deformation is measured by changing the capacitance or electrical resistance of strain-sensitive materials, respectively, show similar characteristics in all parameters

Methods

Results

Conclusion