Linearly Responsive, Reliable, and Stretchable Strain Sensors Based on Polyaniline Composite Hydrogels

Conductive hydrogels are ideal for flexible strain sensors, yet their practical use is often limited by water evaporation, signal hysteresis, and structural instability, which impair linearity, durability, and long-term reliability. To overcome these challenges, we developed a robust multiple-network hydrogel composed of poly(vinyl alcohol) (PVA), polyacrylic acid (PAA), in situ polymerized polyaniline (PANi), and the ionic liquid [EMIM][TFSI]. The resulting composite exhibits an exceptional linear piezoresistive response across its entire working range—from rest to fracture strain of 290%—together with high conductivity (0.68 S/cm), fast response/recovery (0.34 s/0.35 s), and a maximum gauge factor of 2.78. Mechanically robust (tensile strength ≈ 3.7 MPa, modulus ≈ 1.3 MPa), the hydrogel also demonstrates outstanding cyclic durability, withstanding over 12,000 stretching–relaxation cycles, and markedly improved dehydration resistance, retaining about 60% of its mass after 3 days at room temperature. This work provides a holistic material solution for developing high-performance, reliable strain sensors suitable for wearable electronics and soft robotics.