Fabrication and Investigation on Mechanical, Electrical, and Sensing Performance of Polydimethylsiloxane/Carbon Nanotube and Thermoplastic Polyurethane/Carbon Nanotube Wearable Strain Sensors

Abstract

Recent interest in stretchable electronics and wearable technology has driven the demand for flexible and stretchable strain sensors. Conductive polymer composites have gained increasing attention as strain sensors owing to their potential advantages. In this study, the effect of different polymer matrices and varying carbon nanotube (CNT) loadings by fabricating sandwich-structured polydimethylsiloxane (PDMS)/CNT and thermoplastic polyurethane (TPU)/CNT strain sensors is investigated using a solution mixing process. The uniform dispersion of CNTs in both PDMS/CNT and TPU/CNT nanocomposites facilitates proper electrical conductivity. PDMS/CNT6% and TPU/CNT6% strain sensors demonstrate higher linear performance under monotonic strains up to 20% compared to other samples. In cyclic stress–strain tests, PDMS/CNT strain sensors perform more efficiently and have an immediate response compared to TPU/CNT strain sensors, which exhibit the shoulder peak phenomenon. This phenomenon occurs due to the mechanical properties and hysteresis of TPU matrices. In these findings, it is revealed that the relative standard deviation % (RSD%) values of PDMS/CNT strain sensors are smaller than TPU/CNT, which confirms the considerable repeatability of PDMS/CNT strain sensors. Furthermore, PDMS/CNT6% offers effective detection of human body motion, such as finger joint movements with different bending angles and wrist joint bending at various bending rates. In the present study, a guideline is provided for material selection for fabricating flexible strain sensors.