Biochar-Augmented Semi-interpenetrating Network Hydrogel for Multifunctional Applications

Developing multifunctional integrated composites is crucial for next-generation flexible wearable devices. In this study, a multifunctional composite hydrogel was fabricated by incorporating biochar (BC) and polypyrrole (PPy) based on sodium alginate (SA) and polyacrylamide (PAM) to simultaneously enhance mechanical performance, deformation sensing capability, and electromagnetic interference (EMI) shielding effectiveness. The results demonstrated that the synergistic effect of BC and PPy improved the strength and toughness of the hydrogel, which was attributed to the strong interfacial interactions between the fillers and the polymer network, including hydrogen bonding, π-π stacking, and electrostatic interactions. Also, the stability of electrical signal response and attenuation of electromagnetic waves of the composite hydrogel were enhanced by the three-dimensional conductive network formed by BC and PPy. Among all composite hydrogels, the composite hydrogel containing 30 wt % BC exhibited the optimal overall performance with a tensile strength of 0.20 MPa, a tensile modulus of 0.056 MPa, an elongation at break of 874.26%, a tensile toughness of 0.58 MJ·m-3, and an EMI shielding effectiveness of 29.50 dB. The composite hydrogel developed in this study integrates structural stability, strain-sensing capability, and EMI shielding performance, providing a strategy for the design of multifunctional flexible wearable devices.