| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Biomaterial Interfaces | Monday Sessions |
| Session BI-MoE |
| Session: | Biofouling |
| Presenter: | MaryNora Dickson, University of California, Irvine |
| Authors: | MN. Dickson, University of California, Irvine E. Liang, University of California, Irvine N. Vollereaux, University of California, Irvine CA. Choe, University of California, Irvine AF. Yee, University of California, Irvine |
| Correspondent: | Click to Email |
It has been found that the nanopillars on cicada wings are inherently antibacterial, irrespective of surface chemistry (Ivanova et al., Small, 2012). Thus, fabrication of devices presenting such nanostructures would obviate the requirement for any special surface chemical modification. Nano- and microstructured antibacterial surfaces have been previously proposed, including the Sharklet microstructured film (Chung et al.,2007), black silicon (Ivanova et al., 2013) and multi-scale wrinkled polymer films (Freschauf et al., 2012); none of these approaches can be used on ordinary polymer surfaces or easily scaled up. Thus, we endeavored to apply industrial nanostructring techniques to generate biomimetic antibacterial nanostructures at the surfaces of ordinary polymers: poly(methylmethacrylate) (PMMA) polycarbonate (PC). To begin, we replicated the nanopillars of a cicada wing utilizing a double imprinting process. First we molded the pillars in hard polydimethylsiloxane (hPDMS) and applied a backing of PDMS to produce pliable elastomeric stamps presenting a large area (diameter 15 mm) of nanoholes. Next, we utilized either dropcasting of polymer solution or thermal imprinting into a polymer thin film to generate fields of polymer pillars. Dropcasting was used for experiments that required a large area of pillars, since the natural curvature of the cicada’s wing precludes large-area thermal imprinting into flat polymer thin-films. In contrast, thermal imprinting generated very flat, thin, pillared polymer films, which were more suitable for our light transmission microscopy experiments. To make the nanopatterning technique more industrially viable and generate a larger patterned area, we next employed nanoimprint lithography. A commercially available antireflective stamp (Holotools, Germany) with a nanopillared pattern very similar to that of the cicada’s wing, and was used to imprint large, flat, nanostructured polymer thin films. In contaminated aqueous environments, our nanopillared surfaces 1) exhibited reduced surface adhesion of live E. coli determined by a standard fluorescence based viability assay, and 2) killed these bacteria, as evidenced by a decrease in colony forming units in suspension over time (up to 24 hours). Surface chemistry played a minor role. Our surfaces could be used for a wide variety of environmental and medical applications, including surgical trays / instruments and door handles (which function in air), and for implantable medical devices or catheter tubes (which function in aqueous environments).