Ultrasound-driven wettability transition of superhydrophobic composite coating modified magnesium alloys with good corrosion resistance and antibacterial properties

Recently, superhydrophobic magnesium (Mg) alloys are extensively investigated due to their promising applications in corrosion protection and resistance to bacterial adhesion. However, superhydrophobic surfaces may not be conducive to the osteogenic effect of the coated Mg alloys, which limits their clinical application as implants. Herein, the lauric acid (LA)/MoS2/Hydroxyapatite (HA) (LMH) superhydrophobic composite coatings were synthesized on AZ31B Mg alloy by hydrothermal process and hydrophobic treatment. The coated Mg alloy had favorable superhydrophobicity, as evidenced by a contact angle measurement of approximately 151.8°. After 3 minutes of ultrasonic treatment, the contact angle of the coated Mg alloy decreased from 151.8° to 63.5°, which was attribute to the sonothermal effect that changes the surface energy of the coating, hereby removing the air layer at the superhydrophobic interface. Compared to the bare Mg alloy, the electrochemical impedance of the LMH-2.0 superhydrophobic composite coating increased by two orders of magnitude to 89.611 ± 0.593 kΩ·cm2. In vitro antibacterial tests showed that the antibacterial efficiency of LMH-2.0 superhydrophobic coating against both S. aureus and E. coli is more than 99% with the assistance of ultrasonic. Meanwhile, the cell fluorescence staining experiments exhibited that the superhydrophobic coating featuring convertible wettability exhibited promising early cell growth and adhesion. The superhydrophobic coatings with wettability transition on magnesium alloys are expected to be ideal modification coatings for degradable implant materials.