On-Demand Gas-to-Liquid Process To Fabricate Thermoresponsive Antimicrobial Nanocomposites and Coatings

Antimicrobial material is emerging as a major component of the mitigation strategy against microbial growth on abiotic surfaces. In this work, a newly designed process is proposed to fabricate thermoresponsive antimicrobial nanocomposites (TANs) and coatings (TACs) as an on-demand system. Thermoresponsive polymer (TRP)-incorporated silver (Ag) nanocomposites with silica nanoparticles (SNPs) or carbon nanotubes (CNTs; Ag-SNP@TRP or Ag-CNT@TRP) were produced by a single-pass gas-to-liquid process. The SNPs or CNTs were first produced by spark ablation and successively injected for dispersal in a liquid cell containing polydimethylsiloxane, poly(N-isopropylacrylamide), and silver nitrate under ultrasound irradiation. Suspensions of Ag-SNP@TRP or Ag-CNT@TRP nanocomposites were then deposited on a touch screen panel (TSP) protection film via electrohydrodynamic spray to form transparent antibacterial coatings. Fundamental antibacterial activities of TANs were evaluated against Escherichia coli and Staphylococcus epidermidis. The TANs showed stronger antibacterial activities at the higher temperature for all testing conditions. Lower minimum inhibitory concentrations of Ag-SNP@TRP and Ag-CNT@TRP nanocomposites were required against the two bacteria at 37 °C compared to those at 27 °C. The TACs on display showed elevated antimicrobial activity when the panel was turned on (38.1 °C) compared with when the panel was turned off (23.8 °C). This work provides a utilizable concept to continuously fabricate TANs and TACs, and it specifically offers stimuli-sensitive control of antimicrobial activity on TSPs, including other frequently touched surfaces.