Internal Damage Evolution in Double-Network Hydrogels Studied by Microelectrode Technique

Superwetting Gels: Wetting Principles, Applications, and Challenges

Along with the in-depth understanding of wetting behaviors in nature, superwetting gels have received a lot of attention in the past decade. The viscoelasticity of gel materials makes wetting characteristics different from those of rigid materials and brings diverse functionality. In this Review, we summarize the current progress in principles of gel wettability from two aspects: wetting on gels and wetting of gels. Distinct from rigid substrates, the viscoelasticity and solid-liquid coexistence of gel materials introduce additional factors, including surface tension and deformation, resulting in various wetting phenomena. Besides, the similarity between gels and tissues broadens its applications in biomedical devices and smart interfacial regulation. We further conclude the current application that utilizes superwetting gels. Finally, we provide our perspective for future research directions.

Mussel-inspired ultra-stretchable, universally sticky, and highly conductive nanocomposite hydrogels

Developing ultra-stretchable, universally sticky, and highly conductive nanocomposite hydrogels without doping agents and nanoparticle-aggregation is still a challenge. Herein, doping-free and nanoparticle-aggregation-inhibited hydrogels composed of Fe3+, dopamine (DA), pyrrole (Py) and polyacrylic acid (PAA) were prepared. Polypyrrole-polydopamine (PPy-PDA)/PAA hydrogels were quickly formed due to the abundant ionic bonds and physical cross-linking under the addition of Fe3+. Moreover, the H+ ions of the carboxylic acid groups on the PAA polymer chain helped to improve the conductivity of the hydrogels. Surprisingly, the multi-functional hydrogels received a high stretchability of 1900%, a tissue-like elastic modulus of 22 kPa, an adhesive strength of 2125.9 J m-2, and a high conductivity of 0.39 S m-1. Besides, the PPy-PDA/PAA hydrogels showed good antioxidant activity, biocompatibility and tissue repairing behavior. In short, the prepared multi-functional hydrogels have potential to address the human clinical problem of tissue repair and regeneration.