Muscle-Inspired Anisotropic Hydrogels via Pre-Stretching for Direction-Sensitive Human Motion Monitoring

Traditional hydrogels often exhibit disordered molecular structures, resulting in limited mechanical strength, toughness, and functionality, which restrict their practical applications. Here, we engineer an anisotropic $\mathrm{Zr^{4+}}$-crosslinked P(DMA-AA)-CMC hydrogel via pre-stretching to mimic muscle-like alignment. This strategy enhances mechanical strength (5.6 MPa along orientation axis, $1.8\times$ higher than perpendicular) and directional sensitivity through $\mathrm{Zr^{4+}}$-stabilized microstructural ordering. The sensor achieves 303\% $\Delta R/R_0$ at 100\% strain with $2.2\times$ higher sensitivity parallel to pre-stretch direction, enabling precise movement/orientation tracking. It maintains stability over 200 cycles and accurately monitors joint kinematics (e.g., elbow/knee flexion). This biomimetic design advances wearable sensors for human-machine interfaces.