Multifunctional conductive hydrogels with layered polydopamine-coated polyaniline for high-sensitivity small-deformation flexible sensing
Hydrogels hold promising application prospects in flexible sensing due to their flexibility, biocompatibility, and capability to provide a wet environment. For small strain sensing in health monitoring, hydrogels must possess high conductivity and strong adhesion to achieve high sensitivity. To meet these requirements, this work utilized dopamine to self-assemble and encapsulate polyaniline (PANI) in alkaline solutions (pH=10), forming a structure of polydopamine (PDA) layers coating PANI (PDA@PANI). This enhanced the hydrophilicity and dispersion of PANI as a hydrogel conductive additive, improved charge transfer efficiency, increased conductivity, and introduced PDA for superior hydrogel adhesion properties. A dynamic redox system using gallic acid (GA), Fe 3 + , and hydrogen peroxide generates hydroxyl radicals and quinone/semiquinone radicals at room temperature, initiating acrylic acid polymerization to form Fe y (GA/PAA) hydrogels. Incorporating the PDA@PANI solution into this system significantly improves both adhesion and conductivity. The resulting PDA 0.04 @PANI-Fe 0.2 (GA/PAA) hydrogels contain numerous dynamically reversible bonds, demonstrating favorable energy dissipation. These hydrogels exhibit a maximum tensile strength of 131.14 kPa, self-adhesion strength of 30.85 kPa, and conductivity of 0.92 S m −1 . They also possess self-healing, ultraviolet-blocking, and antibacterial attributes. As wearable strain sensors, the hydrogels adhere well to human skin, converting deformation, particularly small strain, into relative resistance changes. They exhibit high sensitivity, good reproducibility, and rapid response characteristics, making them effective for monitoring human movement. Therefore, this preparation strategy holds significant potential for wearable sensors designed to detect small human motion.
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