Field-Emitted Silver Ions at Atmospheric Pressure: Antibacterial Activity and Penetration Into Artificial Skin

Silver (Ag⁺) ions are field-emitted under atmospheric pressure from a sharpened Ag⁺ ion-conductive glass by applying a high voltage. This study investigates the antibacterial efficacy of emitted Ag⁺ ions. When Ag⁺ ions are irradiated onto hydroxyapatite (HAP) for 5 min, an antibacterial effect against Escherichia coli is clearly observed. Furthermore, Ag⁺ ion irradiation directly into the E. coli suspension results in a significant reduction in viable E. coli after 24 h of incubation, compared to immediately after ion irradiation. Although Ag⁺ ions are expected to rapidly lose energy upon collision with air molecules, penetration exceeding 100 μm into the hydrated agar gel is confirmed. When Ag⁺ ions are irradiated onto the surface of an artificial skin (3D reconstructed human epidermis model), fungal cells located beneath the skin are successfully eliminated. These results demonstrate, for the first time, that field-emitted Ag⁺ ions under atmospheric conditions exhibit potent antimicrobial activity.