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Building long-lasting antimicrobial and clean surfaces is one of the most effective strategies to inhibit bacterial infection, but obtaining an ideal smart surface with highly efficient, controllable, and regenerative properties still encounters many challenges. Herein, we fabricate an ultrathin brush–hydrogel hybrid coating (PSBMA-P(HEAA-co-METAC)) by integrating antifouling polyzwitterionic (PSBMA) brushes and antimicrobial polycationic (P(HEAA-co-METAC)) hydrogels. The smart bacterial killing–releasing properties can be achieved independently by the opposite volume and conformation changes between the swelling (shrinking) of P(HEAA-co-METAC) hydrogel layer and the shrinking (swelling) of PSBMA brushes. The friction test reveals that both METAC and SBMA components support great lubrication. By tuning the initial organosilane (BrTMOS:KH570) ratios, the prepared PSBMA-P(HEAA-co-METAC) coating exhibits different antibacterial abilities from single “capturing–killing” to versatile “capturing–killing–releasing.” Most importantly, 99% of the bacterial-releasing rate can be easily achieved via 0.5 M NaCl treatment. This smart surface not only possesses long-lasting antibacterial performance, only ∼1.09 × 105 cell·cm−2 bacterial residue even after 72 h exposure to bacteria solutions, but also can be regenerated and triggered between water and salt solution multiple times. This work provides a new way to fabricate antibacterial smart hydrogel coatings with bacterial “killing–releasing” functions and shows great potential for biomedical applications.

Plasma synthetic jet (PSJ) is widely employed in flow control due to its advantages of zero-mass and fast-response. A novel measurement method for high-frequency dynamic drag variation was adopted in a Mach 8 wind tunnel experiment, demonstrating that the opposing PSJ can achieve a maximum drag reduction of 40.27% and an average drag reduction of 13.25% within one discharge cycle. Subsequently, the numerical method was verified in detail and the effects of different discharge energies and nozzle diameters on the drag reduction characteristics of the opposing PSJ were studied. The results show that an increase in discharge energy is beneficial for the drag reduction characteristics of the opposing PSJ, although the efficiency remains relatively low. In contrast, increasing the nozzle diameter enhances the average drag reduction but significantly reduces the duration of effective control. The drag reduction mechanism of the opposing PSJ can be attributed to the combined effects of pushing the strong bow shock away to form a weaker oblique shock, followed by the reattachment of the shock downstream. [ABSTRACT FROM AUTHOR]

Although diverse uranium (U) adsorbents have been explored, it is still a great challenge for high-efficient uranium extraction form seawater. Herein a wood-mimetic oriented porous Ti3C2Tx-MXene/gelatin hydrogel (MGH) has been explored through growing directional ice crystals cooled by liquid nitrogen and subsequently forming pores by freeze-dry (Ice-template) method, for ultrafast and high-efficient U-adsorption from seawater with great enhancement by both electric field and sunlight. Different from disperse Ti3C2Tx-MXene powder, this MGH not only can be easily utilized but also can own ultrahigh specific surface area for high-efficient U-adsorption. The U-adsorbing capacity of this MGH (10 mg) can reach 4.17 mg·g−1 after only 1 week in 100 kg of seawater, which is outstanding in existing adsorbents. Furthermore, on the positive pole of 0.4 V direct current source or under 1-sun irradiation, the U-adsorbing capacity of the MGH can increase by 57.11% and 13.57%, respectively. Most importantly, the U-adsorption of this hydrogel can be greatly enhanced by simultaneously using the above two methods, which can increase the U-adsorbing capacity by 79.95% reaching 7.51 mg·g−1. This work provides a new biomimetic porous MXene-based hydrogel for electric field/sunlight bi-enhanced high-efficient U-extraction from seawater, which will inspire new strategy to design novel U-adsorbents and systems.