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Traditional hydrogels with soft and wet features often show poor mechanical properties due to their single cross‐linked network and amorphous structure. Hence, there are still great challenges in the preparation of strong and elastic hydrogels with superior lubrication performance for broader applications. Inspired by the biphasic structure of natural cartilage, the tough layered P(AM‐AA)‐Fe3+ (poly(acrylamide‐co‐acrylic acid)‐Fe3+) hydrogels are prepared via a sodium citrate treatment‐induced surface dissociation approach. The top lubricating layer with porous structure and high water content can achieve ultra‐low friction (friction coefficient [COF] ~ 0.010 at 5 N load), whereas the bottom stiff layer with compact structure demonstrates excellent load‐bearing capacity. The layered structure could provide hydrogels with excellent physical functions such as high strength (~7.1 MPa), superior lubrication (COF ~ 0.018, 10 N), and wear resistance (COF < 0.05, 5 N, 18,000 cycles), thereby expanding the application of hydrogel in the field of bioinspired lubrication materials. [ABSTRACT FROM AUTHOR]

Biomimetic hydrogel lubrication coatings with high wettability and low friction show great promise in tissue engineering, wound dressing, drug delivery, and intelligent sensing. Inspired by the hierarchical structure of natural cartilage, a layered hydrogel coating was constructed to functionalize rigid polyetheretherketone (PEEK). The layered hydrogel coating features a structural design comprising a top soft layer and a middle robust layer. The porous structure of the top soft hydrogel layer stores water molecules, providing surface lubrication, while the dense structure of the middle robust hydrogel layer offers load-bearing capacity. These synergistic effects of the gradient hydrogel layer endow the PEEK substrate with an ultra-low coefficient of friction (COF~0.010 at 5 N load), good load-bearing capacity (COF~0.031 at 10 N load), and excellent wear resistance (COF < 0.05 at 5 N load after 20,000 sliding cycles). This study introduces a novel design paradigm for robust hydrogel coatings with exceptional lubricity, displaying the potential application in cartilage replacement materials. [ABSTRACT FROM AUTHOR]

Conductive polymer composites are highly demanded for practical application in electromagnetic interference shielding and Joule heating owing to their excellent flexibility and adjustable conductivity. Herein, a thin film with a gradient structure, comprising carbon nanotube/castor oil‐based waterborne polyurethane (CNT/WPU), has been fabricated through solution mixing utilizing casting technology. Scanning electron microscopy images confirm that CNTs are enriched at the top of the obtained CNT/WPU film, leading to a low resistance value. Consequently, the resultant gradient CNT/WPU films exhibit shielding effectiveness, specific shielding effectiveness, and an absorption coefficient of 22.8 dB, 1091 dB/cm, and 0.697, respectively, indicating a predominance of absorption in the shielding capacity. The temperature at the surface of the resultant gradient CNT/WPU film reaches ~77°C at a voltage of 20 V. The film with a CNT content of 14.1 wt% exhibits a good stress of 11.7 MPa and a high module of 39.9 MPa. Therefore, the obtained CNT/WPU films can be applied as thin shielding materials or coating. Highlights: Fabricating a gradient CNT/castor oil–based waterborne polyurethane films.Exhibiting shielding effectiveness of 22.8 dB and A‐value of 0.697.Steady‐state temperature of CNT/WPU reaches 77°C at 20 V.Possessing green EMI shielding capability. [ABSTRACT FROM AUTHOR]