A. Sachan, R.J. Narayan
North Carolina State University,
United States
Keywords: thin films, pulsed laser deposition, plasma-enhanced chemical vapor deposition (
Summary:
Healthcare-associated infections have a significant impact on patient morbidity and mortality. The formation of microbial biofilms on medical device surfaces presents a technological challenge, as biofilms confer enhanced resistance to antimicrobial agents and immune activity compared to planktonic bacteria. The presentation considers the use of three thin film deposition techniques for antimicrobial applications, namely pulsed laser deposition (PLD), matrix-assisted pulsed laser evaporation (MAPLE), and atomic layer deposition (ALD). PLD involves laser ablation of a target material using high-energy laser pulses (typically krypton fluoride excimer lasers at 248 nm) in a vacuum chamber, which generates an energetic plasma plume containing species with kinetic energies ranging from 100-1000 kT. The technique is associated with the congruent transfer of material composition from the target to the substrate. PLD processing allows films with controlled thickness and low roughness to be deposited on medically-relevant surfaces. MAPLE is a variant of PLD for depositing films of pharmaceutical agents and other organic materials. The process involves laser evaporation of a frozen target, which contains the organic material dissolved in a volatile solvent. During deposition, the solvent preferentially absorbs laser energy; the pharmacologic agent molecules are ejected from the target via kinetic energy transfer during collisions. The MAPLE deposition parameters include laser wavelengths of 248 or 193 nm, and laser fluence values of 0.05-0.25 J/cm². This approach allows for the deposition of heat-sensitive compounds such as pharmaceutical agents and other organic materials. The ALD process involves sequential and self-limiting chemical reaction, which enables the coating of surfaces with complex geometries. The process alternates exposure to different precursors separated by purge periods to prevent gas-phase reactions. The use of ALD to deposit zinc oxide coatings on nanoporous aluminum oxide substrates was described. Plasma-enhanced chemical vapor deposition (PECVD) was used to deposit silicon-doped diamond-like carbon (Si-DLC) coatings; tetramethylsilane was used as the precursor gas for these studies. The substrate temperature was maintained at ambient conditions during the coating process, which allowed for coatings to be deposited on polymer surfaces. Post-processing treatments using argon or oxygen plasma were used to modify the surface chemistry and wettability of the coatings. This presentation considers the processing and in vitro characterization of the engineered thin films. These engineered thin films offer opportunities for addressing healthcare-associated infections.