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Device-associated infection is one of the significant challenges in the biomedical industry and clinical management. Controlling the initial attachment of microbes upon the solid surface of biomedical devices is a sound strategy to minimize the formation of biofilms and infection. A synergistic coating strategy combining superhydrophobicity and bactericidal photodynamic therapy is proposed herein to tackle infection issues for biomedical materials. A multifunctional coating is produced upon pure Mg substrate through a simple blending procedure without involvement of any fluoride-containing agents, differing from the common superhydrophobic surface preparations. Superhydrophobic features of the coating are confirmed through water contact angle measurements (152.5 ± 1.9°). In vitro experiments reveal that bacterial-adhesion repellency regarding both Gram-negative (Escherichia coli) and Gram-positive ( Staphylococcus aureus) strains approaches over 96%, which is evidently ascribed to the proposed synergistic strategy, that is, superhydrophobic nature and microbicidal ability of photodynamic therapy. Electrochemical analysis indicates that the superhydrophobic coating provides pronounced protection against corrosion to underlying Mg with 80% reduction in the corrosion rate in minimum essential medium and retains the original surface features after 168 h exposure to neutral salt spray. The proof-of-concept research holds a great promise for tackling the notorious bacterial infection and poor corrosion resistance of Mg-based biodegradable materials in a simple, efficient, and environmentally benign manner.

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Styrene-butadiene rubber (SBR) is currently the main material for manufacturing passenger car tire treads due to excellent mechanical properties. The SBR is usually subjected to vulcanization treatment to improve the performance. This work uses molecular dynamics simulation to study the uniaxial stretching process of SBR with different cross-linking degrees, and analyzes the relationship between its molecular chain structures and mechanical properties. The results show that the cross-linked SBR model begins to deform plastically when the strain reaches 2.2, and there is no overall breaking within the limited deformation (≤4). Instead, it presents the characteristics of continuous partial breaking. Through the energy analysis, the deformation of the SBR system is mainly to overcome the energy required for the transformation of the non-oriented chain structure to the straight chain structure and the continuous stretching of the chain. In the cross-linked system, the increase in bond energy and bond angle energy associated with cross-linking dramatically increases the total energy of the system, thereby affecting the overall mechanical properties. In addition, temperature and strain rate have significant effects on the tensile properties of the cross-linked SBR system. Especially, the increase in the cross-linking degree reduces the temperature dependence of its stress-strain behavior.

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