A remarkably ultra-sensitive large area matrix of MXene based multifunctional physical sensors (pressure, strain, and temperature) for mimicking human skin

Abstract

Electronic skin has attracted a lot of interest in recent years due to its ability to mimic human skin and also its excellent conformability. Even though there are reports on electronic skin, the major issue that still needs to be resolved is achieving multifunctional sensing at the same time as ultra-high sensitivity. Hence, there is an immediate requirement to develop inexpensive, highly sensitive, and superior performance piezoresistive multifunctional sensors that mimic skin. Herein, an as synthesized pure MXene (Ti₃C₂T_x) colloidal solution was used to deposit a thin film on flexible polyurethane foam, forming a three-dimensional conductive network with an ultra-high sensitivity of ∼34.24 kPa⁻¹ (1.477–3.185 kPa of applied pressure range) and an elevated gauge factor of ∼323.59 (5–20% of applied strain range). Further merits such as reproducibility, low cost, high scalability, and excellent stability after 2500 cycles imply the sturdiness of the fabricated device. The remarkable sensing efficiency can be attributed to the strong interaction of Ti₃C₂T_x and PU foam, the inherent 3D network of PU coupled with the excellent electrical properties of Ti₃C₂T_x, and the interconnection of the unconnected branches present in the internal framework of PU-foam, which indicates the existence of more conduction paths. Besides, the fabricated Ti₃C₂T_x was deposited on cellulose paper to be utilized as a temperature sensor which displayed ∼2.22 × 10⁻³ °C⁻¹ TCR and 29.43 meV activation energy. Lastly, real time applications for the fabricated device are investigated including detecting an unknown position of an object and human gestures. The successful demonstration of the low-cost, flexible Ti₃C₂T_x based piezoresistive sensor has shown innovative applications in biomedical, security, educational, and health sectors.