Bio-inspired antimicrobial surfaces fabricated by glancing angle deposition

I-GLAD: a new strategy for fabricating antibacterial surfaces

The paper uses inverted glancing angle deposition (I-GLAD) for creating antibacterial surfaces. Antibacterial surfaces are found in nature, such as on insect wings, eyes, and plant leaves. Since the bactericidal mechanism is purely physical for these surfaces, the antimicrobial resistance of bacteria to traditional chemical antibiotics can be overcome. The technical problem is how to mimic, synthesize, and scale up the naturally occurring antibacterial surfaces for practical applications, given the fact that most of those surfaces are composed of three-dimensional hierarchical micro-nano structures. This paper proposes to use I-GLAD as a novel bottom-up nanofabrication technique to scale up bio-inspired nano-structured antibacterial surfaces. Our innovative I-GLAD nanofabrication technique includes traditional GLAD deposition processes alongside the crucial inverting process. Following fabrication, we explore the antibacterial efficacy of I-GLAD surfaces using two types of bacteria: Escherichia coli (E. coli), a gram-negative bacterium, and Staphylococcus aureus (S. aureus), a gram-positive bacterium. Scanning electron microscopy (SEM) shows the small tips and flexible D/P (feature size over period) ratio of I-GLAD nanoneedles, which is required to achieve the desired bactericidal mechanism. Antibacterial properties of the I-GLAD samples are validated by achieving flat growth curves of E. coli and S. aureus, and direct observation under SEM. The paper bridges the knowledge gaps of seeding techniques for GLAD, and the control/optimization of the I-GLAD process to tune the morphologies of the nano-protrusions. I-GLAD surfaces are effective against both gram-negative and gram-positive bacteria, and they have tremendous potentials in hospital settings and daily surfaces.

Cicada Wing-Inspired Transparent Polystyrene Film Integrating Self-Cleaning, Antifogging, and Antibacterial Properties

A transparent film integrating antifouling, antifogging, and antibacterial properties is crucial for its application as a protective mask, goggles, or lens. Herein, applying dynamic injection molding coupled with a bionic gradient template, a fast and efficient method is proposed for the preparation of the bionic polystyrene surface (BNPPS) with a cicada wing-inspired nanopillar structure. The contact angle of the BNPPS film increases continuously along the wing vein, while the sliding angle decreases continuously, mimicking the gradient wetting state of a cicada wing and providing excellent self-propelled removal properties for tiny water droplets. Notably, the BNPPS film has a transmittance higher than 90% and a reflectivity lower than 5% in the visible light range. Dyeing water, milk, juice, cola, and ink can slide smoothly from the BNPPS film surface without leaving any residue. Importantly, the nanopillars on the BNPPS film surface can penetrate and kill most of the Escherichia coli within 20 min. Therefore, the prepared BNPPS film with sufficient mechanical strength gathers the unique properties of the cicada wing together. The proposed research is expected to offer valuable guidance for fabricating self-cleaning, antifogging, and antibacterial optical devices that could be utilized in medical and vision systems operating in harsh environments.