Changes in the Antibacterial Performance of Polymer-Based Nanocomposites Induced by Additive Manufacturing Processing

The idea supporting the investigation of the current manuscript was to develop customized filters for air conditioners with different pore percentages and geometry with the additional advantage of presenting antibacterial performance. This property was expected due to the reinforcement of Cu nanoparticles in the polymeric matrix of poly(lactic acid) (PLA) and polyurethane (TPU). The filaments were characterized by their chemical composition, thermal and mechanical properties, and antibacterial behavior before and after processing by fused filament fabrication. An X-ray photoelectron spectroscopy showed that the nanocomposite filaments presented Cu particles at their surface in different valence states, including Cu⁰, Cu⁺, and Cu²⁺. After processing, the metallic particles are almost absent from the surface, a result confirmed by micro-computer tomography (μ-CT) characterization. Antibacterial tests were made using solid-state diffusion tests to mimic the dry environment in air conditioner filters. The tests with the nanocomposite filaments showed that bacteria proliferation was hindered. However, no antibacterial performance could be observed after processing due to the absence of the metallic element on the surface. Nevertheless, antimicrobial performance was observed when evaluated in liquid tests. Therefore, the obtained results provide valuable indications for developing new nanocomposites that must maintain their antimicrobial activity after being processed and tested in the dry conditions of solid-state diffusion.