The in-situ forming injectable hydrogels hold great potential for the treatment of irregular wounds. However, their practical applications were hindered by long gelation time, poor mechanical performance, and lack of...
Fibrous patches capable of withstanding bursting force and recruiting endogenous stem cells are of great demand for wound treatment. A programmable strategy for development of radially gradient nanofibrous patches with rapid deployment property, robust bursting bearing capability, and excellent mesenchymal stem cell (MSC) recruitment capability, is demonstrated. Benefiting from the royal water lily‐like radially branched architecture, the gradient fibrous (GF) patches exhibit fast deployment in aqueous solution (2 s), high bursting strength of 4.6 N, as well as “center‐to‐periphery” gradient immobilization of stromal‐cell‐derived factor 1α (SDF1α). The SDF1α gradient patches direct MSC migration from the periphery to the center along the aligned nanofibers, resulting in a 4.2 times higher migrated cell number and 2.6 times greater maximum migration distance than random fibrous patches with homogenous SDF1α. The gelatin methacryloyl coated GF patches respond to matrix metalloproteinase‐9 for “on‐demand” release of anti‐inflammatory drug diclofenac sodium (DS). Furthermore, repair of the mouse full‐thickness skin incision validates that SDF1α/DS/GF patches are able to provide feasible microenvironment to attenuate inflammation and improve endogenous MSC recruitment, leading to accelerated wound healing. This work may open a new pathway for development of smart tough fibrous patches for stimulating endogenous repair mechanisms during tissue regeneration.
An extended microbridge test (eMBT) was proposed to assess the adhesion of metallic coatings on metallic substrates. Through loading on the backside of narrow striped freestanding coatings, a two-dimensional stable interfacial delamination was introduced. A cross-sectional scanning electron microscope (SEM) was used to examine the interfacial fracture process. A large deflection solution for elastic deformation of the coating was derived, and an approximate model was established for the estimate of interfacial crack extension force G. The eMBT samples of electroplated Ni coatings on C45 carbon steel substrate were tested, and the measured interfacial fracture toughness was about 5.28 J/m2. Cross-sectional SEM examination showed that the interface crack extended along the interface plane, and therefore the interfacial fracture proceeded by the debonding of Ni/steel interface.
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