Mechanically robust and conductive poly(acrylamide) nanocomposite hydrogel by the synergistic effect of vinyl hybrid silica nanoparticle and polypyrrole for human motion sensing

Hydrogel-based sensors are playing important roles in artificial intelligence, benefiting from its flexibility and biocompatibility, whereas conventional hydrogels are fragile and electronically insulated in nature. To overcome these obstacles, in this work, a facile way was proposed by using vinyl hybrid silica nanoparticle (VSNP) as the crosslinker and in situ polymerized polypyrrole (PPy) as the conductive agent. The results showed that the tensile strength, the elongation at break, and the compression strength could be enlarged to 447 kPa, 1340%, and 5.56 MPa with only 0.16 wt. % of VSNPs. More importantly, benefiting from the formation of the unique “honeycomb” structure, the introduction of dopamine-modified PPy (DA@PPy) not only elevated the conductivity of hydrogel to 0.06 S/m but also further enhanced the tensile strength, the elongation at break, and the compression strength of 541 kPa, 1415%, and 7.27 MPa as the molar concentration of DA@PPy was 0.4 mol/L. Cyclic tests proved that the as-prepared PAM/VSNPs/DA@PPy hydrogels were able to tolerant 2000 cyclic stretching and 500 cyclic compressions. In addition, during the cyclic test, the relative change of the resistance is sensitive to a wide stretching strain range (1–300%) and a compression strain range (up to 90%), making the hydrogels excellent candidates for strain sensors. The wide strain range and high sensitivity ensure that the PAM/VSNPs/DA@PPy hydrogels could capture not only subtle small strain facial movement but also large strain wrist bending. This work provides a new and convenient approach for the development of mechanically robust and conductive poly(acrylamide)-based nanocomposite hydrogel for human motion sensing. Graphical abstract Mechanically robust and conductive poly(acrylamide) nanocomposite hydrogel is prepared for human motion sensing.