Silver and copper ions are well-established antimicrobial agents that combat bacteria, viruses, fungi, and algae. Recently, Corning Incorporated (Corning, N.Y.) researchers discussed the importance of microbial suppression for glass-based touch surfaces on smartphones, ATMs, etc.¹ They demonstrated that silver “bullets” can be ion exchanged into borosilicate glass, resulting in surfaces that effectively control growth of Escherichia coli bacteria. To accomplish exchange, Corning immersed glass in a melt of AgNO₃–alkali nitrate at 300°C–400°C. Similarly, Borsella et al.² used CuSO₄–alkali sulfate melts at 518°C–570°C to ion exchange copper into glass slides.

Refractron Technologies Corp. (Newark, N.Y.) manufactures two classes of ceramics: structural zirconias based on dense magnesium-partially-stabilized zirconia (Mg-PSZ) and yttria tetragonal-zirconia polycrystal (YTZP); and alumina (brown- and white-fused grits), silica, and mullite ceramics with precisely controlled porosity (Figure 1). Most of the latter products are bonded with one of several proprietary silicate glasses. These products function as fine bubble diffusers that oxygenate, purify, and filter water in numerous applications. They also transfer gases to liquids under controlled flow for fish farms, aquatic plants, beverages, and aquariums. In addition, saturating the porosity of these materials with ink produces fingerprint touch surfaces.