Flexible antibacterial strain sensor with low electrical hysteresis, ultralow detection limit, and wide linear sensing range for human motion monitoring and human–machine interaction

Abstract

Achieving low electrical hysteresis, an ultralow detection limit, and a wide linear sensing range is critical for the practical application of flexible strain sensors. However, the intrinsic viscoelasticity of the elastomer macromolecules can adversely affect the behavior of the conductive sensing network during stretching and relaxation, rending it challenging to simultaneously achieve these properties. Herein, a novel strategy is proposed to design a hybrid covalent-ionic crosslinking network within the elastomer and to construct a robust conductive carbon nanotube (CNT) layer on the elastomer surface using a swelling-driven penetration method. The hybrid crosslinking network gives the elastomer enhanced mechanical strength and exceptional stretchability, while reducing the dynamic losses of the macromolecules. It also reduces the impact of the elastomer macromolecules on the conductive layer during stretching. Even minimal strains are sufficient to induce slippage of the CNTs, leading to changes in resistance. As the strain increases, further disentanglement and slippage of the CNTs results in crack formation, which enables greater resistance variation and dominates the sensing mechanism. As a result, the as-prepared conductive elastomer-based strain sensors exhibit exceptional sensing performance, including low electrical hysteresis (2.3 %), ultralow detection limit (0.1 %), wide linear working range (690 %), and excellent durability (>10,000 cycles). The strain sensors have been successfully employed in human motion monitoring, human–machine interaction, and angle measurement. In addition, the incorporation of the ionic crosslinking network endows the sensor with excellent antibacterial properties. Consequently, the developed conductive elastomers hold significant promise for applications in smart wearable electronics.