Tissue-adhesive, stretchable, and self-healable hydrogels based on carboxymethyl cellulose-dopamine/PEDOT:PSS via mussel-inspired chemistry for bioelectronic applications

A new generation of wearable devices using hydrogel-based sensors has attracted attention for human motion monitoring detection. On the other hand, integrating multiple properties, such as self-adhesiveness, repeatable adhesion, stretchability, high conductivity, good mechanical performance, and good electrical stability within a single hydrogel, which remains a challenge. In this study, hydrogels composed of borate crosslinked pendant catechol groups of carboxymethyl cellulose-dopamine conjugate (CMC-DA) in a polyacrylamide (PAM) crosslinked network (CDB-PAM) were developed. The stretchability (2763%) and tensile strength (36.9 ± 2.3 KPa) of the CDB-PAM hydrogel were improved when 4 wt% of CMC-DA was used for hydrogel preparation. The incorporation of 2.0 wt% PEDOT:PSS greatly improved the tensile stress (44.9 ± 2.6 KPa), low elastic modulus (3.1 ± 0.15 KPa), and stretchability (2873%). The CDB-PAM-PEDOT:PSS hydrogel had self-healing and recoverable properties. The hydrogel demonstrated self-adhesive properties (e.g., skin adhesion to porcine skin 65.1 ± 2.2) with long-term reusability by maintaining redox-active catechol groups in the hydrogel. The in vitro biocompatibility test using skin fibroblasts and keratinocytes cells confirmed the good biocompatibility of the hydrogels. The PEDOT:PSS-incorporated CDB-PAM hydrogel showed good conductivity (41.6 S/m) because of the charge transfer between PEDOT and catechol/quinone groups of CMC-DA in the hydrogel, forming a well-connected electric path. Furthermore, the developed hydrogel-based strain sensor was sensitive to human flexible wearable devices in bioelectronic applications. Overall, the hydrogel with multiple properties, such as high stretchability, self-healing, and high conductivity, demonstrated promising for flexible wearable devices in bioelectronic applications.