Enhanced erosion resistance of biopolymer-enriched B. subtilis NCIB 3610 biofilms

<p>Erosion resistance is one of the advantages bacteria gain by producing biofilms. While it is undesirable for us humans when biofilms grow on medical devices or industrial pipelines, biofilms with a high erosion resistance can be advantageous for biotechnological applications. Here, we demonstrate how the erosion resistance of <em>B. subtilis</em> NCIB 3610 biofilms can be enhanced by integrating foreign (bio)polymers such as γ-polyglutamate (PGA), alginate and polyethylene glycol (PEG) into the matrix during biofilm growth.<br /><br />Artificial enrichment of the NCIB 3610 biofilms with these biopolymers causes a significant increase in the erosion resistance by slightly changing the surface topography: A decreased cavity depth on the surface results in an alteration in the mode of surface superhydrophobicity, and we obtain a state that is located somewhere between rose-petal like and lotus-like wetting resistance. Surprisingly, the viscoelastic and microscopic penetration properties of the biofilms are not affected by the artificial incorporation of (bio)polymers. As we obtained similar results with all the biopolymers tested (which differ in terms of charge and molecular weight), this indicates that a variety of different (bio)polymers can be employed for a similar purpose.<br /><br />The method introduced here may present a promising strategy for engineering beneficial biofilms such, that they become more stable towards shear forces caused by flowing water but, at the same time, remain permeable to nutrients or other molecules.</p>

Controllable magnetic roughness surface with sustainable superhydrophobicity based on magnetorheological colloid

In this article, magnetorheological colloid was adopted to coat a stainless steel substrate, which was cured under magnetic field to form magnetic roughness surface. Superhydrophobicity had been verified in the experiments, and the influential factors on the hydrophobic performance had been explored. A regular sawtooth structure model was proposed to relate the hydrophobicity with the formed surface microstructure. With the self-cleaning and bonding strength testing, the magnetic roughness surface is promising to keep sustainable superhydrophobicity in the self-cleaning or drag reduction applications.

Metal ions weaken the hydrophobicity and antibiotic resistance of Bacillus subtilis NCIB 3610 biofilms

Surface superhydrophobicity makes bacterial biofilms very difficult to fight, and it is a combination of their matrix composition and complex surface roughness which synergistically protects these biomaterials from wetting. Although trying to eradicate biofilms with aqueous (antibiotic) solutions is common practice, this can be a futile approach if the biofilms have superhydrophobic properties. To date, there are not many options available to reduce the liquid repellency of biofilms or to prevent this material property from developing. Here, we present a solution to this challenge. We demonstrate how the addition of metal ions such as copper and zinc during or after biofilm formation can render the surface of otherwise superhydrophobic B. subtilis NCIB 3610 biofilms completely wettable. As a result of this procedure, these smoother, hydrophilic biofilms are more susceptible to aqueous antibiotics solutions. Our strategy proposes a scalable and widely applicable step in a multi-faceted approach to eradicate biofilms.

Two-dimensional MXene-reinforced robust surface superhydrophobicity with self-cleaning and photothermal-actuating binary effects

A robust superhydrophobic surface with high performances of photothermal-conversion and light-driven motion has been fabricated by integrating with hydrophobic two-dimensional MXenes.

TiO 2 nanowire-templated hierarchical nanowire network as water-repelling coating

Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO 2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO 2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO 2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

Triple phase boundary induced self-catalyzed growth of Ge–graphite core–shell nanowires: field electron emission and surface wettability

Ge–graphite core–shell nanowires with good field electron emission capability and surface superhydrophobicity were synthesized by triple phase boundary-induced self-catalyzed growth.