Integrating proteins into a hydrogel network enables its good bioactivity as an ECM environment in biorelative applications. Although extensive studies on preparing protein hydrogels have been carried out, the reported systems commonly present very low mechanical strength and weak water-rentention capacity. Learning from the astringent mouthfeel, we report here a protein engineered multinetwork physical hydrogel as TA-PVA/BSA. In a typical case, the BSA protein-integrated poly(vinyl alcohol) (PVA) solution is treated by the freeze-thaw method and forms the first hydrogel network, and tannic acid (TA) then cross-links with BSA proteins and PVA chains to form the secondary hydrogel network based on the noncovalent interaction (hydrogen bond and hydrophobic interaction). The as-prepared TA-PVA/BSA composite hydrogel is a pure physically cross-linking network and possesses ultrahigh tensile strength up to ∼9.5 MPa but is adjustable, relying on the concentration of TA and BSA. Moreover, its mechanical strength is further improved by prestretching induced anisotropy of mechanical performance. Because of its controllable and layered structure as skin, the composite hydrogel presents good water-retention capacity compared to traditional high strength hydrogels. This work demonstrates a novel method to design high mechanical strength but layered physical cross-linking hydrogels and enables us to realize their biorelative applications.

Preventing ice formation and ice swift removal from the solid surface are essential in numerous application fields. Superhydrophobic coating is an effective way to delay the icing phenomenon. However, the superhydrophobic coating was wetted easily after icing−deicing cycles that led to the failure of anti-icing. In this study, a robust, amphiphobic coating consisted of fluorinated multiwalled carbon nanotubes (FMWCNTs) and commercial polyurethane was constructed by a simply spray process. Because of the addition of FMWCNTs, the coating demonstrated a good amphiphobic feature and highly efficient photothermal conversion, which endowed the coating surface with excellent deicing and defrosting characteristics under sunlight irradiation. In addition, self-cleaning and self-healing properties of the coating under sunlight ensured its efficient photothermal conversion and long service life. To further improve the photothermal deicing effect, a coating system containing a photothermal layer (P), thermal-conductive layer (C), and thermal-protective layer (P) was constructed. The heat generating from the photothermal layer can transfer the whole coating surface by the conductive layer, but with limited transmission to substrate materials by a thermal-protective layer. The coating system can still deice and defrost rapidly on the whole surface and only a small portion of photothermal coating was irradiated under extremely low temperature. The outdoor experiment has confirmed that the coating melted and removed snow rapidly in a winter environment. The multifunctional photothermal deicing coating may have a wide application in outdoor surrounding.

Controllably coating the surfaces of substrates/medical devices with hydrogels exhibits great application potential, but lacks universal techniques. Herein, a new method, namely ultraviolet‐triggered surface catalytically initiated radical polymerization (UV‐SCIRP) from a sticky initiation layer (SIL) (SIL@UV‐SCIRP), is proposed for growing hydrogel coatings. The method involves three key steps: 1) depositing a sticky polydopamine/Fe3+ coating on the surface of the substrates‐SIL, 2) reducing Fe3+ ions to Fe2+ ions as active catalysts by UV illumination with the assistance of citric acid, and 3) conducting SCIRP in a monomer solution at room temperature for growing hydrogel coatings. In this manner, practically any substrate's surface (natural or artificial materials) can be modified by hydrogel coatings with controllable thickness and diverse compositions. The hydrogel coatings exhibit good interface bonding with the substrates and enable easy changes in their wettability and lubrication performances. Importantly, this novel method facilitates the smooth growth of uniform hydrogel lubrication coatings on the surface of a range of medical devices with complex geometries. Finally, as a proof‐of‐concept, the slippery balls coated with hydrogel exhibited smooth movement within the catheter and esophagus. Hence, this method can prove to be a pioneering universal modification tool, especially in surface/interface science and engineering.

Ice formation is a common phenomenon that brings security risks in numerous fields. A superhydrophobic surface can greatly delay icing time due to its liquid repellence feature, but it fails under cold and humid conditions. In this work, a photo‐thermal@electro‐thermal superhydrophobic coating (PESC) consisting of electric‐conductive carbon nanotubes (ECNTs) and fluoro‐modified polyacrylate is constructed by means of spray to realize both anti‐icing and de‐icing simultaneously. Traditional ECNTs not only provide hierarchical micro‐nano structures to construct superhydrophobic surfaces for anti‐icing, but also guarantee de‐icing capacity because of solar‐thermal and electric‐thermal effects. In warm daytime, enough heat is generated by solar‐thermal conversion to keep the temperature of the coating surface above zero to achieve anti‐icing and de‐icing. On a cloudy day or extremely cold day, the coating also can stay warm to prevent icing, owing to photo‐thermal and electric‐thermal dual effects. And during the cold nighttime, the coating is heated to prevent icing after it is electrified as a result of electric‐thermal effects. The PESC system can reduce electricity consumption from the maximum, fulfilling eco‐friendly and energy saving concepts. This functional superhydrophobic coating with anti‐icing and swift de‐icing performance may have broad application prospects in the power industry.

Hydrogels as one kind of soft materials with a typical three-dimensional (3D) hydrophilic network have been getting great attention in the field of biolubrication. However, traditional hydrogels commonly show poor tribology performance under high-load conditions because of their poor mechanical strength and toughness. Herein, pure chemical-crosslinking hydrogels mixed with different types of the micron-scale fibers can meet the requirements of strength and toughness for biolubrication materials, meanwhile the corresponding tribology performance improves significantly. In a typical case, three kinds of reinforcement matrix including needle-punched fibers, alginate fibers, and cottons are separately combined with Poly(n-vinyl pyrrolidone)-poly(2-hydroxyethyl methacrylate (PVP-PHEMA) hydrogels to prepare fibers reinforced composite hydrogels. The experimental results show that the mechanical properties of fibers reinforced composite hydrogels improve greatly comparable with pure PVP-PHEMA hydrogels. Among three kinds of fibers reinforced composite hydrogel, the as-prepared composite hydrogels reinforced with needle-punched fibers possess the best strength, modulus, and anti-tearing properties. Friction tests indicate that the fibers reinforced composite hydrogels demonstrate stable water-lubrication performance comparable with pure PVP-PHEMA hydrogels. Besides, the hydrogel-spunlace fiber samples show the best load-bearing and anti-wear capacities. The improved tribology performance of the composite hydrogels is highly related to mechanical property and the interaction between the fibers and hydrogel network. Finally, spunlace fibers reinforced hydrogel materials with high load-bearing and low friction properties are expected to be used as novel biomimetic lubrication materials.

Inspired by natural living surfaces, researchers have developed many excellent anti-smudge coatings, but there remain some critical challenges such as complex or expensive fabrications, poor long-term stability, non-transparency, etc., which may limit their large-area application. In this work, we designed a robust and transparent omniphobic coating with a one-step dip coating method. The perfluoropolyether chains were grafted on a smooth glass surface, and the coating surface not only presented good liquid repellency and stain resistance but also owned excellent mechanical wear resistance. The stain resistance property and wettability have barely changed after hundreds of thousands of friction cycles in air or even in an organic solvent surrounding. The robust hybrid coating possesses simple preparation, an excellent property, and durability, which may bring a widespread interest in the engineering application field.

In this study, a novel surface initiated polymerization (SIP) method was developed from organic‐inorganic hybrid persistent initiator coating (PIC) that embeds initiator molecules into inorganic silica sol‐gel layer. Comparing with traditional silane initiator surface that prepared by chemical vapor deposition (CVD) method, the PIC can effectively improve the mechanical stability of initiator that was able to endure ten‐thousand times of friction cycles. Besides, it allows polymer grafting from sub‐surface and so the grafted brushes, poly 3‐sulfopropyl methacrylate potassium salt (pSPMA) on the PIC were also much more wear‐resisting than those prepared by the traditional ways. More importantly, the PIC could still trigger new polymerization reaction when the grafted brushes were worn off. In addition, the PIC is universal and can be covered on different substrates including glass, metals and plastics, etc. to realize functionalization of these materials. The approach may pave technological way for the application of surface grafted polymer brushes.

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