Wet-spun hybrid hydrogel fibers exhibiting high electrical and mechanical stability in flexible electronics

Abstract

The ability to alter the crosslinking and network architectures of the three-dimensional polymers in hydrogels has prompted interest in their application in flexible electronics. However, ensuring long-term stability and balancing the mechanical strength and malleability of hydrogel materials remain challenging. This study accordingly synthesized ionic–electronic hydrogel fibers comprising a conductive Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PSS) polymer, a lithium chloride inorganic salt, COOH-functionalized multi-walled carbon nanotubes (CNTs), glycerol, and different weight percentages of polyvinyl alcohol (PVA). First, the numerous advantages of the proposed ∼300 μm diameter hydrogel fibers over bulk hydrogels were detailed. Next, the distinct hybrid organic–inorganic composition of the fibers was shown to maintain steady functioning, with stable ionic conduction, a clear frequency dependent trend and long-term stability. Furthermore, the crosslinking among the PVA, CNTs, and PSS molecules was determined to improve the stability of electrical conductivity. Finally, the fibers withstood strains in excess of 250 % for over six months while sustaining flexibility and functional integrity, and their relative variation in resistance under cyclic strain (1000 cycles) exhibited remarkable durability and dependability. Therefore, the hydrogel fibers were shown to be well-suited to use in commercial-level smart textiles, biomimetic soft robotics, and energy-harvesting applications such as wearable electronic devices.