Piezoelectric Response and Energy Harvesting Capability in a Moldable PVA/PANi Composite Prepared via Frozen-Gel Polymerization

We report a soft, moldable composite based on poly(vinyl alcohol) (PVA) and in situ polymerized polyaniline (PANi), synthesized via a frozen-gel polymerization approach that enables uniform PANi distribution within a hydrogel matrix without thermal processing or mechanical alignment. After drying, the resulting rubbery organic mixed ionic–electronic conductor (OMIEC) exhibits piezoelectric-like behavior under compressive deformation and strain-dependent electrical characteristics suitable for sensing and energy harvesting applications. Mechanical testing revealed compressive and tensile Young’s moduli of ∼0.69 and ∼0.89 MPa, respectively, with high stretchability and viscoelastic hysteresis. Under repeated compressive strain, the composite generated open-circuit voltages up to 0.2 mV/mm and short-circuit current densities of 0.22 μA/mm2, scaling proportionally with strain. Differential resistance analysis and relaxation studies indicated nonohmic behavior, ionic accumulation, and space-charge effects across the metal/polymer interfaces. The material also demonstrated a piezoresistive gauge factor of ∼1.8, with conductivity decreasing predictably under elongation. Power generation studies showed a maximum output of ∼7 nW/cm3 at 1 kΩ resistive load, closely matching theoretical estimates. The composite was integrated into a simple harvesting circuit, successfully charging a 100 μF capacitor and lighting an LED via repeated mechanical input. The results highlight a different class of piezoelectric-like materials derived from maturated hydrogels, offering the potential for soft, biocompatible, and easily processable alternatives to conventional piezoelectric systems. The material’s combined electromechanical response, ease of fabrication, and deformability make it suitable for wearable electronics, soft robotics, and self-powered sensing platforms.