Background: Synthetic hydrogels are commonly mechanically weak which limits the scope of their applications. Methods: In this study, we synthesized an organic-inorganic hybrid hydrogel with ultrahigh strength, stiffness, and toughness via enzyme-induced mineralization of calcium phosphate in a double network of bacterial cellulose nanofibers and alginate-Ca 2+ . Results: Cellulose nanofibers formed the first rigid network via hydrogen binding and templated the deposition of calcium phosphate, while alginate-Ca 2+ formed the second energy-dissipating network via ionic interaction. The two networks created a brick-mortar-like structure, in which the "tortuous fracture path" mechanism by breaking the interlaced calcium phosphate-coated bacterial cellulose nanofibers and the hysteresis by unzipping the ionic alginate-Ca 2+ network made a great contribution to the mechanical properties of the hydrogels. Conclusion:The optimized hydrogel exhibited ultrahigh fracture stress of 48 MPa, Young's modulus of 1329 MPa, and fracture energy of 3013 J/m 2 , which are barely possessed by the reported synthetic hydrogels. Finally, the hydrogel represented potential use in subchondral bone defect repair in an ex vivo model.

Perfluoropolymer membranes are widely used because of their good environmental adaptability. Herein, the ultrafine fibrous FEP porous membranes were fabricated with electrospinning-sintered technology. The effects of PVA content and sintering temperature on the fabricated membranes’ morphologies and properties were investigated. The results indicate that a kind of dimensionally stable network structure was formed in the obtained ultrafine fibrous FEP porous membranes after sintering the nascent ultrafine fibrous FEP/PVA membranes. The optimal sintering conditions were obtained by comparing the membranes’ performance in terms of membrane morphology, hydrophobicity, mechanical strength, and porosity. When the sintering temperature was 300 °C for 10 min, the porosity, water contact angle, and liquid entry pressure of the membrane were 62.7%, 124.2° ± 2.1°, and 0.18 MPa, respectively. Moreover, the ultrafine fibrous FEP porous membrane at the optimal sintering conditions was tested in vacuum membrane distillation with a permeate flux of 15.1 L·m−2·h−1 and a salt rejection of 97.99%. Consequently, the ultrafine fibrous FEP porous membrane might be applied in the seawater desalination field.

Membrane fouling has attracted a lot of attention in the membrane separation field. Herein, we selected the homogeneous-reinforced polyvinylidene fluoride (HMR-PVDF) and heterogeneous-reinforced polyvinylidene fluoride (HTR-PVDF) hollow fiber membranes to investigate the fouling mechanism of membranes in membrane bioreactor (MBR) systems. The filtration models, membrane adsorption experiment, and membrane resistance distribution after a long or short time operation were assessed to compare their antifouling properties in order to verify the optimal membrane. The outer surface, shown by an SEM observation of the HMR-PVDF and HTR-PVDF membranes, was rough and smooth, respectively. Moreover, the HMR-PVDF membranes had a higher adsorption capacity than the HTR-PVDF membranes when an equilibrium state was almost 2.81 times that of the original membrane resistance. A cleaning method (mainly physical and chemical) was utilized to illustrate the operational stability of the membranes. In summary, the HMR-PVDF hollow fiber membrane presented better antifouling properties than the HTR-PVDF membranes, which was conducive to industrial implementation.

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