Highly Sensitive yet Strain-Insensitive Flexible Pressure Sensors Based on MWCNTs/TPU Composites for Wide-Temperature-Range Applications

Abstract

Strain-insensitive flexible pressure sensors can conform to dynamically changing and complex surfaces while avoiding pressure-strain coupling artifacts, making them highly valuable for applications such as monitoring human body activities. However, despite various fabrication methods that have been proposed, large-scale manufacturing remains associated with high cost and low efficiency, and the resulting devices may lose functionality in low-temperature environments. In this study, a large-area MWCNTs/TPU sensor layer was fabricated using a sandpaper template combined with a flame-assisted spray technique, achieving low cost and high sensitivity. A high-modulus polyimide@Au (PI@Au) electrode layer was integrated with a low-modulus, highly elastic, and anti-freezing polyurethane substrate. The resulting sensor exhibits ultrahigh sensitivity (∼629.9 kPa^-1 in the range of 0.3–28 kPa), a fast response time (10 ms), and excellent stability over 1000 repeated cycles. It maintains high sensing accuracy across 0%–50% strain, with sensitivity variations of only ∼5.2 %, ∼4.1 %, and ∼3.6 % between the 0% and 50% strain states in the low-pressure (0.3–28 kPa), medium-pressure (28–80 kPa), and high-pressure (80–320 kPa) ranges, respectively. Reliable signal detection is preserved even at −20 °C under up to 50% strain. This work is expected to facilitate the application of stretchable pressure sensors on deformable interfaces and expand their operational temperature range.