Steve DiSpirito, Bennet Kleinhans, Natalie Page Theodore Scabarozi, Lei Yu, Jeffrey Hettinger, Rowan University, Glassboro, NJ
We report the fabrication and electrochemical characterization of titanium nitride (TiN)–silver (Ag) thin films for on-demand antimicrobial applications. Prior studies have demonstrated that co-deposition of Ag with Ti in a nitrogen-rich reactive atmosphere produces TiN coatings with a columnar microstructure containing interconnected pores between the pillars. These pores host self-assembled Ag nanoparticles that function as a reservoir for Ag-ion release when a potential exceeding the Ag oxidation potential is applied in an electrochemical environment. In this work, phosphate-buffered saline was used to simulate blood plasma conditions. Flow cell work used phosphate-buffered solution as the electrolyte. The primary objective of this study is to estimate the useful antimicrobial lifetime of these coatings by quantifying Ag ion release rates at different stages of depletion. To simulate late-stage Ag exhaustion, bilayer coatings were synthesized consisting of an Ag-containing TiN layer adjacent to the substrate and a second pure TiN capping layer. The thickness of the TiN cap layer was systematically varied by terminating Ag deposition partway through film growth, enabling controlled investigation of diffusion and depletion effects. Electrochemical characterization was conducted using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). In addition, potential- and time-controlled Ag release was monitored using an electrochemical flow cell operated under stepped potentials, allowing real-time evaluation of ion release. The concentration of released Ag ions was quantitatively measured using inductively coupled plasma mass spectrometry, providing release rates correlated with applied voltage and exposure time. The deposition, microstructure and electrochemical results will be discussed in terms of Ag release kinetics, coating longevity, and the influence of TiN cap layer thickness on antimicrobial performance.