DC Magnetron-Generated Reactive Glow Discharge Plasma Activation of Acid-Etched Titanium for Superhydrophilic TiO2-Rich Surfaces

This study addresses the need for controllable physicochemical activation routes for titanium surfaces by developing a hybrid treatment that combines hydrofluoric acid (HF) microtexturing with reactive glow discharge plasma (GDP) generated in a DC magnetron sputtering (DC-MS) system, applied to commercially pure grade 1 titanium. Sequential acid etching induced controlled microstructural roughening, followed by a 1 min plasma exposure in air at 6 × 10–1 Pa to modify the near-surface oxide chemistry while preserving the etched morphology. Acid treatment preferentially dissolved the α-Ti matrix along grain boundaries, producing band-like corrosion grooves and hierarchical microtexturing, whereas plasma activation induced localized oxidation and produced a superhydrophilic response. Eight activation cycles over 150 days of ambient storage repeatedly restored the hydrophilic state, which persisted approximately 16 h per cycle. Raw X-ray diffraction (XRD) and grazing-incidence XRD patterns remained dominated by α-Ti, with no resolved reflections attributable to crystalline TiO2. X-ray photoelectron spectroscopy indicated the formation of a TiO2-rich surface after plasma activation, accounting for 100% of the fitted Ti 2p area, with no detectable F 1s signal. Adsorbed oxygen-containing species accounted for 4.7%, compared with 4.3% for the etched and 17.4% for the cleaned control. Because biological responses were not evaluated, these physicochemical changes should not be interpreted as direct evidence of improved protein adsorption, cellular behavior, bacterial resistance, or in vivo performance. This approach establishes DC-MS-generated GDP activation as a rapid route for titanium surface activation and advanced surface-engineering applications.