MXene-containing anisotropic hydrogels strain sensors with enhanced sensing performance for human motion monitoring and wireless transmission

Conductive hydrogels have attracted great attention for flexible electronics and intelligent sensing. However, conventional hydrogels with isotropic components and structures merely exhibit isotropic sensing properties, while structural orientation and anisotropy are much more common in nature. Inspired by the anisotropic structure of human tissues, we propose a facile and efficient method to fabricate anisotropic conductive hydrogels. This endows the hydrogels with excellent mechanical properties and electrical conductivity compared to conventional isotropic conductive hydrogels. MXene-containing anisotropic hydrogels were prepared by mechanical stretching and exhibit anisotropic mechanical and electrochemical properties based on their anisotropic structure. The tensile stress and toughness along the parallel stretching direction of MXene-containing anisotropic hydrogel can reach 2.68 MPa and 7.99 MJ/m3, respectively, which are significantly higher than those of the hydrogel along the vertical stretching direction and MXene-containing isotropic hydrogel. Moreover, the conductivity of MXene-containing anisotropic hydrogel along the parallel stretching direction (0.096 S/m) is better than that of the hydrogel along the vertical stretching direction and the isotropic hydrogel. MXene-containing anisotropic hydrogels exhibit enhanced strain sensing performance along the parallel stretching direction. Meanwhile, the hydrogel sensors can realize wireless transmission. It is expected that MXene-containing anisotropic hydrogel sensors have wide application prospects in flexible wearable devices.