The emerging 3D printing technique allows for tailoring hydrogel‐based soft structure tissue scaffolds for individualized therapy of osteochondral defects. However, the weak mechanical strength and uncontrollable swelling intrinsic to conventional hydrogels restrain their use as bioinks. Here, a high‐strength thermoresponsive supramolecular copolymer hydrogel is synthesized by one‐step copolymerization of dual hydrogen bonding monomers, N‐acryloyl glycinamide, and N‐[tris(hydroxymethyl)methyl] acrylamide. The obtained copolymer hydrogels demonstrate excellent mechanical properties—robust tensile strength (up to 0.41 MPa), large stretchability (up to 860%), and high compressive strength (up to 8.4 MPa). The rapid thermoreversible gel ⇔ sol transition behavior makes this copolymer hydrogel suitable for direct 3D printing. Successful preparation of 3D‐printed biohybrid gradient hydrogel scaffolds is demonstrated with controllable 3D architecture, owing to shear thinning property which allows continuous extrusion through a needle and also immediate gelation of fluid upon deposition on the cooled substrate. Furthermore, this biohybrid gradient hydrogel scaffold printed with transforming growth factor beta 1 and β‐tricalciumphosphate on distinct layers facilitates the attachment, spreading, and chondrogenic and osteogenic differentiation of human bone marrow stem cells (hBMSCs) in vitro. The in vivo experiments reveal that the 3D‐printed biohybrid gradient hydrogel scaffolds significantly accelerate simultaneous regeneration of cartilage and subchondral bone in a rat model.

Electrocatalytic water splitting is one of the sustainable and promising strategies to generate hydrogen fuel but still remains a great challenge because of the sluggish anodic oxygen evolution reaction (OER). A very effective approach to dramatically decrease the input cell voltage of water electrolysis is to replace the anodic OER with hydrazine oxidation reaction (HzOR) due to its lower thermodynamic oxidation potential. Therefore, developing the low-cost and efficient HzOR catalysts, coupled with the cathodic hydrogen evolution reaction (HER) is tremendously important for energysaving electrolytic hydrogen production. Herein, a new-type copper-nickel nitride (Cu 1 Ni 2 -N) with rich Cu 4 N/Ni 3 N interface is rationally constructed on the carbon fiber cloth. The three-dimensional electrode exhibits extraordinary HER performance with an overpotential of 71.4 mV at 10 mA cm -2 in 1.0 M KOH, simultaneously delivering an ultralow potential of 0.5 mV at 10 mA cm -2 for HzOR in 1.0 M KOH/0.5 M hydrazine electrolyte. Moreover, the electrolytic cell utilizing the synthesized Cu 1 Ni 2 -N electrode as both the cathode and anode displays a cell voltage of 0.24 V at 10 mA cm -2 with an excellent stability over 75 h. The present work develops the promising copper-nickel-based nitride as a bifunctional electrocatalyst through hydrazine-assistance for energy-saving electrolytic hydrogen production.

No abstract

No abstract