Bacterial Cellulose-Stabilized Liquid Metal Enables Stretchable Poly(acrylic acid) Strain Sensor

Conductive hydrogels with simultaneous high stretchability, robust mechanical toughness, and reliable strain-sensing sensitivity remain challenging to fabricate, particularly without toxic chemical initiators or cross-linkers. To address this, a multifunctional poly(acrylic acid)/gallium-bacterial cellulose (PAA/Ga-BC) hydrogel was developed through an initiator-free approach. BC serves simultaneously as an emulsifier to stabilize liquid metal nanoparticles (LMNPs) in aqueous suspension and as a rigid reinforcing scaffold within the PAA matrix, yielding a physically cross-linked dual-network structure governed by hydrogen bonds, Ga3+ ionic coordination, and polymer chain entanglement. The optimized PAA/Ga1.0-BC0.5 hydrogel achieves a tensile strength of 155 kPa, an elongation at break of 1869%, and a toughness of 1.28 MJ·m–3. As a strain sensor, it exhibits a gauge factor (GF) of 4.8 over the 500–800% strain range, detects strains as low as 1%, and retains stable cyclic performance over 300 stretching cycles at 75% strain. The hydrogel also demonstrates rapid electrical self-reconnection (200 ms), mechanical recovery exceeding 90% after 6 h, broad substrate adhesion (up to 6.4 kPa on wood), and measurable antibacterial inhibition against both S. aureus and E. coli. Furthermore, the hydrogel undergoes water-triggered disintegration within 21 days. This work establishes a platform for high-performance flexible strain sensors applicable to wearable human motion detection and emerging soft robotics.