Acid-reorganized PEDOT:PSS/Deep eutectic solvent gels for highly conductive and stretchable strain sensing

Deep eutectic solvent (DES)-based gels provide a useful platform for soft conductors because their hydrogen-bonded liquid phase can be fixed in compliant polymer networks. For strain sensors, however, many DES gels still show conductivities close to 1 S/m, which limits resistance readout under dynamic deformation. Here, PEDOT:PSS was incorporated into a choline chloride/glycerol/poly(N-hydroxyethyl acrylamide) eutectogel, followed by concentrated H 2 SO 4 treatment after gel formation. The optimized CGN-1.5PPH gel exhibits a conductivity of 1750 S/m approximately 1.8 × 10 3 times that of pristine CGN (0.96 S/m), while retaining a high deformation capability with a tensile strength of 0.28 MPa and an elongation at break of 569%. FTIR, XRD, and SEM analyses indicate that acid treatment weakens PEDOT-PSS association, changes the bonding environment around PSS and PNHEMAA, and promotes PEDOT-rich ordered domains. The resulting compact conductive pathways give clear responses to 5-20% cyclic strains, a working range up to 150%, gauge factors of 0.17, 0.23, and 0.59 over three strain regions, stable output over 1000 cycles at 100% strain, and a response time of 20 ms. In a badminton-serve demonstration, the sensor distinguishes arm internal-rotation motions in real time. These results show that acid-assisted PEDOT reorganization markedly enhances electrical transport in DES-based stretchable conductors while preserving sufficient deformability for large-strain sensing applications.