Interfacial Sintering of PU/MXene Foam for Piezoresistive Sensor with Superior Sensitivity, Mechanical Performance, and Durability

High sensitivity, good mechanical property, and durability are critical parameters to value piezoresistive sensing performance, which highly rely on the interfacial interaction between the conductive filler and the polymer matrix. Using polydopamine (PDA) to improve the interfacial interaction is the usually adopted manner. However, unsatisfactory sensing performance is afforded, resulting from the formation of inhomogeneous deposition of PDA on the polymer matrix. In this work, for the first time, a piezoresistive sensor comprising anisotropic PU foam with a tightly adhered MXene conductive layer (MXene@PU) is fabricated by microwave sintering. The strong interfacial adhesion induced by microwave sintering coupled with the stress–strain amplification effect imparted by the aligned parallel channels of the directional TPU foams results in trinity excellence in sensitivity, mechanical performance, and durability. As a result, the as-fabricated sensor delivers a high sensitivity of 0.109 kPa–1, an impressive gauge factor of 7.78, and an excellent mechanical property with a compressive strength of 1603 kPa at 80% strain, which is 11.1 times, 16.2 times, and 1.6 times that of PDA-treated traditional ones, respectively. Moreover, superior durability is demonstrated for the MXene@PU foam sensor even under macropressure or macrostrain, which is a big challenge for conductive nanomaterial-coated polymer matrix-derived sensors. This novel approach provides a practical methodology for architecting a high-performance piezoresistive sensor that is very attractive in the intelligent sensing field.