The design of superhydrophobic stainless steel surfaces by controlling nanostructures: A key parameter to reduce the implantation of pathogenic bacteria.

Reducing bacterial adhesion on substrates is fundamental for various industries. In this work, new superhydrophobic surfaces are created by electrodeposition of hydrophobic polymers (PEDOT-F4 or PEDOT-H8) on stainless steel with controlled topographical features, especially at a nano-scale. Results show that anti-bioadhesive and anti-biofilm properties require the control of the surface topographical features, and should be associated with a low adhesion of water onto the surface (Cassie-Baxter state) with limited crevice features at the scale of bacterial cells (nano-scale structures).

Flagella but not type IV pili are involved in the initial adhesion of Pseudomonas aeruginosa PAO1 to hydrophobic or superhydrophobic surfaces.

Over the last decades, surface biocontamination has become a major concern in food industries and medical environments where its outcomes could vary from financial losses to public health issues. Understanding adhesion mechanisms of involved microorganisms is essential to develop new strategies of prevention and control. Adhesion of Pseudomonas aeruginosa, a nosocomial pathogenic bacterium, relies on several bacterial features, among which are bacterial appendages such as flagella and type IV pili. Here, we examine the role of P. aeruginosa PAO1 flagella and type IV pili in the adhesion to abiotic surfaces with various hydrophobicities. Adhesion kinetics showed, that after 60min, flagella increased the adhesion of the strain to surfaces with high hydrophobicity while no effect was observed on hydrophilic surfaces. Flagella of adherent bacteria exhibited specific and conserved pattern on the surfaces that suggested a higher affinity of flagella for hydrophobic surfaces. Based on these results and on previous studies in the literature, we proposed a model of flagella-mediated adhesion onto hydrophobic surfaces where these appendages induce the first contact and promote the adhesion of the bacterial body. These findings suggest that anti-bioadhesive surface design should take into consideration the presence of bacterial appendages.

Superoleophobic Meshes with Relatively Low Hysteresis and Sliding Angles by Electropolymerization: Importance of Polymer-Growth Control.

To study the effects of polymer growth and polymer nanostructure formation on stainless-steel meshes (opening size of 100 µm), we report the behavior of three electrodeposited polymers with varied deposition charge to achieve superoleophobic meshes with low adhesion (low hysteresis (H) and sliding angles (α)). We show the importance of controlling the polymer growth around the mesh wires (two-dimensional growth) to avoid the re-covering of the mesh openings. Indeed, both the polymer micro-/nanostructures as well as the presence of the holes are necessary to highly reduce the solid-liquid contact area and to achieve superoleophobic properties with low adhesion. Herein, with the best polymer, superoleophobic properties are obtained with apparent contact angles of 160° for sunflower oil (H=13°, α=10°), 155° for hexadecane (H=29°, α=30°), 143° for dodecane (sticking behavior), and 134° for decane (sticking behavior).

Superoleophobic Meshes with Relatively Low Hysteresis and Sliding Angles by Electropolymerization: Importance of Polymer-Growth Control.

Invited for this month's cover is the group of Prof. Frederic Guittard from Université Nice Sophia-Antipolis. The cover picture shows a superoleophobic stainless-steel mesh obtained by electrodeposition of fluorinated conducting polymers. Read the full text of the article at 10.1002/cplu.201300315.