Controlled Ag release from electrically conductive coating systems

Abstract

Nowadays, silver (Ag) coatings find widespread use in medical textiles, e.g. wound bandages, mainly due to their antibacterial properties related to the Ag ion release in aqueous media. Moreover, Ag-coated fibers offer excellent electrical properties, allowing their use for sensing applications such as electrocardiography (ECG) belts. Due to the potential cytotoxicity of Ag, electrically conductive coating systems need to be developed with reduced and time-controlled Ag release.In this study, pure silver was continuously deposited onto a polyester (PET) fiber to optimize electrical conductivity for ECG application. The pure silver coated fibers, however, showed the typical initial burst release of Ag ions when immersed in an aqueous environment locally yielding cytotoxic conditions, i.e. high Ag ion concentrations. While the ion release can be favourable for antibacterial properties, it needs to be limited for medical devices. A diffusion barrier is thus required, while maintaining the electrical conductivity. Thus, different plasma polymer top coatings were applied onto the Ag-coated fibers using a continuous deposition process. The functional plasma polymerized films (a-C:H and a-C:H:O) were compared with an ultrathin titanium oxide layer (as recently investigated) regarding electrical properties and silver release. Ag release measurements demonstrated that an efficient control over the release properties (initial burst and long-term release) was achieved depending on the hydrophobicity and thickness of the plasma polymer films.