Micro-nanostructured polymer surfaces using injection molding : a review

Micro injection molding is in great demand due to its efficiency and applicability for industry. Polymer surfaces having micro-nanostructures can be produced using injection molding. However, it is not as straightforward as scaling-up of conventional injection molding. The paper is organized based on three main technical areas: mold inserts, processing parameters, and demolding. An accurate set of processing parameters is required to achieve precise micro injection molding. This review provides a comparative description of the influence of processing parameters on the quality of final parts and the precision of final product dimensions in both thermoplastic polymers and rubber materials. It also highlights the key parameters to attain a high quality micro-nanostructured polymer and addresses the contradictory effects of these parameters on the final result. Moreover, since the produced part should be properly demolded to possess a high quality textured polymer, various demolding techniques are assessed in this review as well

Application of superhydrophobic coatings as a corrosion barrier : a review

This review provides an overview of recent advances in the application of superhydrophobic surfaces to act as corrosion barriers. The adverse consequences of corrosion are a serious and widespread problem resulting in industrial plant shutdowns, waste of valuable resources, reduction in efficiency, loss or contamination of products, and damage to the environment. Superhydrophobic surfaces, inspired by nature, can be considered as an alternative means for improving the protection of metals against corrosion. Due to the possibility of minimizing the contact area between liquids and a surface, superhydrophobic surfaces can offer great resistance to corrosion. Artificial superhydrophobic surfaces have been developed with the potential of being applied in numerous settings including self-cleaning, anti-icing, oil-water separation, and especially anti-corrosion applications. In this paper, we review the concept of superhydrophobicity through presentation of different theoretical models. The fabrication and application of superhydrophobic surfaces are presented, and we then discuss the use of superhydrophobic coatings as barriers against the corrosion of metals

On the oil repellency of nanotextured aluminum surface

Two different superhydrophobic surfaces were elaborated and their oil repellency behavior was evaluated using several liquid with different surface tension. A silicone rubber/SiO2 nanocomposite coated (A) on aluminum substrate by “spin-coating" and the sample B was an anodized aluminum surface covered by Teflon-like coating. A high static contact angle about ∼162° was measured for two prepared surfaces on which the water droplet rolloff. Scanning electron microscopy (SEM) showed the presence of micro/nanostructures for both sample A and B similar to that of lotus leaf. However the sample A presented significantly different behaviour of wettability against the low surface tension liquid. Sample A has been wetted totally by oil (dodecan) droplet while sample B showed oleophobic behaviour. Oleophobic property of Teflon like coating can be contributed to the presence of CF2 and CF3 functional group which was shown by XPS analysis

Superhydrophobic micro-nanofibers from PHBV-SiO2 biopolymer composites produced by electrospinning

Electrospinning is a relatively simple technique for producing continuous fibers of various sizes and morphologies. In this study, an intrinsically hydrophilic poly(3-hydroxybutarate-co-3-hydroxyvalerate) (PHBV) biopolymer strain was electrospun from a solution under optimal processing conditions to produce bilayers of beadless micro-fibers and beaded nano-fibers. The fibrous mats produced from the pure PHBV solution exhibited hydrophilicity with complete wetting. Incorporation of polydimethylsiloxane (PDMS) treated silica into the electrospinning solutions resulted in a non-wetting state with increased fiber roughness and enhanced porosity; however, the fiber mats displayed high water droplet-adhesion. The SiO2–incorporated fibrous mats were then treated with stearic acid at an activation temperature of 80 °C. This treatment caused fiber surface plasticization, creating a tertiary hierarchical roughness owing to the interaction of PHBV chains with the polar carboxyl groups of the stearic acid. Scanning electron microscopy was used to assess the influence of the electrospinning process parameters and the incorporation of nanoparticles on surface morphology of the fibers; energy dispersive X-ray spectroscopy confirmed the presence of SiO2 nanoparticles. Fourier transform infrared spectroscopy was performed to study the incorporation of SiO2 and the interaction of stearic acid with PHBV at various concentrations. The chemical interaction between stearic acid and PHBV was confirmed, while SiO2 nanoparticles were successfully incorporated into the PHBV fibers at concentrations up to 4.5% by weight. The incorporation of nanoparticles and plasticization altered the thermal properties of PHBV and a decrease in crystalline fraction was observed. The stearic acid modified bilayers produced from the micro-nano-fibrous composites showed very low water droplet sticking, a roll off angle of approximately 4° and a high static contact angle of approximately 155° were achieved

Design strategies for antiviral coatings and surfaces: A review

The routine disinfection and sanitization of surfaces, objects, and textiles has become a time-consuming but necessary task for managing the COVID-19 pandemic. Nonetheless, the excessive use of sanitizers and disinfectants promotes the development of antibiotic-resistant microbes. Moreover, that improper disinfection could lead to more virus transfer, which leads to more viral mutations. Recently developed antiviral surface coatings can reduce the reliance on traditional disinfectants. These surfaces remain actively antimicrobial between periods of active cleaning of the surfaces, allowing a much more limited and optimized use of disinfectants. The novel nature of these surfaces has led, however, to many inconsistencies within the rapidly growing literature. Here we provide tools to guide the design and development of antimicrobial and antiviral surfaces and coatings. We describe how engineers can best choose testing options and propose new avenues for antiviral testing. After defining testing protocols, we summarize potential inorganic and organic materials able to serve as antiviral surfaces and present their antiviral mechanisms. We discuss the main limitations to their application, including issues related to toxicity, antimicrobial resistance, and environmental concerns. We propose solutions to counter these limitations and highlight how the context of specific use of an antiviral surface must guide material selection. Finally, we discuss how the use of coatings that combine multiple antimicrobial mechanisms can avoid the development of antibiotic resistance and improve the antiviral properties of these surfaces

Optimization of ground icing protection for aircraft: Snow endurance tests, rheological analysis and thermography of anti-icing fluids

Poster presentation at the colloquium seminar, arranged by Université du Québec à Chicoutimi (UQAC), Chicoutimi, 11.10.2023

A comparative study of the icephobic and self-cleaning properties of Teflon materials having different surface morphologies

Materials having fluorocarbon bonds are among the best candidates for the fabrication of superhydrophobic surfaces. Here, we describe two facile, non-expensive, and industrialized approaches to produce superhydrophobic Teflon materials having ultra-water repellency, icephobic, and self-cleaning properties. Direct replication and plasma-treatment approaches produced Teflon sheets having very different surface patterns, i.e. microstructures and micro- nanostructures. Neither approach altered the chemical composition of the original Teflon surfaces. Rice leaf–like microstructures were produced on the replicated surface, whereas lotus leaf–like hierarchical micro-nanostructures characterized the plasma-treated surface. Water droplets rolled off the micro-nanostructured surfaces ~10% faster than off the microstructured surfaces. The micro-nanostructured surface also produced more rebounds for a water droplet during the impact test. Although both surfaces possessed similar self-cleaning properties, the micro-nanostructured surface reduced ice adhesion to a greater degree than the microstructured surface. The more effective ice repellency of the micro-nanostructured surface was due to its surface morphology that reduced the interlocking of ice inside the surface asperities. However, the microstructured surface delayed considerably the onset of freezing of a water droplet due to the larger micro-air pockets trapped within its surface asperities

Rigorous testing to assess the self-cleaning properties of an ultra-water-repellent silicone rubber surface

Ultra-water-repellent silicone-based surfaces were produced to study their self-cleaning properties. First, we investigated the consistency of the micro-nano air pockets that are present between the surface asperities responsible for the formation of the Cassie-Baxter regime. We then performed a comprehensive series of self-cleaning experiments involving both dissolved and non-dissolved contaminants using various materials (e.g., kaolin, carbon black, silica, etc.) and contaminant-applying methods (e.g., dropwise, spraying, wet or dry contaminants). In this paper, the self-cleaning tests were arranged from the less severe, i.e., non- dissolved contamination tests, to more severe, i.e., wet dissolved contamination test, and ending with the most severe, i.e., dry dissolved contamination test. Due to the ultra-low contact angle hysteresis, the produced surfaces showed favorable self-cleaning properties against the various types of contaminants and the different means of contaminant application. The produced surfaces retained their water repellency properties following application of the contaminants and after the cleaning of the surfaces, thus verifying the self-cleaning performance and resistance of the fabricated superhydrophobic silicone surfaces

Direct replication of micro-nanostructures in the fabrication of superhydrophobic silicone rubber surfaces by compression molding

We describe a simple method for fabricating superhydrophobic high temperature vulcanized (HTV) silicone rubber surfaces by direct replication using a compression molding system. The resulting rubber samples possessed micro-nanostructures on the surface. This micro- and nano- scale roughness produced a water contact angle of >160º and a contact angle hysteresis of <3º. The roughness patterns on chemically etched aluminum surfaces, which served as templates, were successfully replicated on the rubber surfaces. An antistiction coating applied to the template surface ensured that the rubber was completely removed during demolding and that the replicated micro-nanostructures on the silicone surface were preserved. Surface roughness of the aluminum templates was optimized at HCl concentrations of 15 wt.%, with a lower roughness value observed at acid concentrations above and below this value. The developed HTV silicone rubber surfaces also demonstrated a freezing delay and a self-cleaning capacity