Tannic Acid‐Enhanced PVA /Sodium Alginate Dual‐Network Hydrogel for Wearable Strain Sensors

Abstract

This work presents the design and fabrication of a conductive dual‐network hydrogel for flexible strain sensing applications. The hydrogel is constructed from two interpenetrating networks: the first formed by hydrogen‐bonded tannic acid (TA) and polyvinyl alcohol (PVA), and the second created via Ca 2+ ‐mediated ionic crosslinking of sodium alginate (SA). Structural characterization by SEM confirms the formation of an integrated dual‐network architecture, where abundant hydroxyl groups in TA synergistically interact with both the PVA network and SA chains, significantly enhancing mechanical toughness and strength. Notably, the resulting SA/PVA/TA hydrogel exhibits strong adhesion to diverse substrates—including iron, glass, plastic, and human skin (e.g., finger joints)—without the need for additional adhesives. Upon immersion in CaCl 2 solution, both tensile strength and electrical conductivity increase with crosslinking time. The hydrogel crosslinked for 30 min achieves a tensile strength of 0.234 MPa and an elongation at break of 126%. Real‐time resistance measurements during mechanical deformation demonstrate a stable and sensitive response to strain, confirming its suitability as a wearable strain sensor. This study thus introduces a simple yet effective strategy for developing adhesive, stretchable, and conductive hydrogels for next‐generation flexible electronics.