Flexible conductive hydrogels through optimized interfacial connectivity of hybrid fillers toward efficient electromagnetic interference shielding and wearable strain sensors

Conductive hydrogels hold significant potential in wearable flexible sensors and electromagnetic interference (EMI) shielding materials owing to their tissue-mimetic mechanical compliance and water-rich porous structures. However, simultaneously achieving high EMI shielding efficiency (SE) and excellent mechanical properties remain a challenge. To address this issue, we present a hybrid conductive network strategy within the hydrogel system through incorporating carbon nanotubes and nickel-coated graphite into a hydrogel matrix. The resulting composite hydrogel demonstrates remarkable stretchability, reliability, and anti-fatigue capability, owing to the synergistic combination of the multi-dimensional filler network, abundant hydrogen bonds and electrostatic interactions within the gel network. More importantly, profiting from the synergy of moderate conductivity and internal water-rich environment of the gel, the composite hydrogel at a thickness of 2 mm exhibits an exceptional EMI SE of 58 dB in the X-band, which is superior to most of the EMI shielding hydrogels reported to date. In addition, integrating the hydrogel sensor with machine learning, precise and stable gesture recognition and remote control are realized with an accuracy of up to 100%. This work offers a novel perspective for advancing flexible hydrogel sensor technologies and underscores their vast potential in intelligent wearable devices, superb EMI shielding materials, and human-machine interactions.