Instantaneous deposition of super-hydrophilic Ti/TiOx coating with multiscale-nanoparticle stacked structure via directionally atmospheric metal plasma jet

Abstract

Super-hydrophilic coatings, valued for their multifunctionality in anti-fogging, antibacterial activity, and lubrication, have garnered significant research interest across industrial applications. We present a rapid and efficient fabrication method of metal oxide super-hydrophilic coating utilizing electrical explosion methodology. High-velocity dense plasma jets (∼km/s) are generated and directed toward silicon substrates for impact deposition. During the preparation, a metallic wire undergoes ultra-rapid heating (∼10⁴ K in μs, dT/dt ∼ 10¹⁰ K/s) and quenching, with discharge energy (200–500 J) inversely governing nanoparticle size. Notably, three-dimensional nanoparticle networks extending up to 350 nm from the substrate surface (at 500 J energy) are observed. This nano-structural evolution elevates surface roughness increasing from 119 to 181 nm, and accordingly the contact angle decreasing from 4.37^±0.86°to 1.85^±1.09°. XPS analysis confirms that the oxidation of Ti can be in a shallow surface of the coating as TiO and Ti-OH. The modified surfaces demonstrated exceptional functional persistence, maintaining hydrophilicity (contact angle <10°) after 24-h ambient exposure. Furthermore, the methodology demonstrates satisfactory versatility, as evidenced by Al/AlO_x coatings synthesized under identical experimental conditions, exhibiting contact angle ranges from 5.94^±0.43° to 3.16^±0.17°.