Mussel-Inspired Adhesive and Carbon Fiber Conductive Hydrogel for Flexible Sensors

Conductive hydrogels, which are considered to be a promising material for human motion detection sensors, often display low flexibility, limited elongation, and non-adhesive properties. Herein, a multifunctional hydrogel with self-adhesive, highly stretchable, and conductive properties was developed by introducing polydopamine (DA) and carbon fiber (CF) into polyacrylamide (PAAm) hydrogel. The DA was polymerized with oxygen to form polydopamine (PDA), and the PDA-CF-PAAm hydrogel was hybrid-crosslinked with covalent bonds and recoverable non-covalent bonds including hydrogen bonds and π-π stacking. Therefore, the prepared PDA-CF-PAAm hydrogel exhibits high and reversible stretchability. Additionally, the hydrogel demonstrates high adhesiveness on various substrate surfaces, such as paper, glass, rubber, and biological tissue surfaces due to the catechol groups of PDA. Furthermore, the obtained PDA-CF-PAAm hydrogel is conductive because of the addition of CF. As a result, the self-adhesive, highly stretchable, and conductive PDA-CF-PAAm hydrogel can be directly adhered to the skin as a strain sensor to monitor human body motion. This work may expand the scope of multifunctional hydrogel preparation for flexible wearable devices.