Ultra-low friction, superhydrophobic, plasma micro-nanotextured fluorinated ethylene propylene (FEP) surfaces

Analysis of time-dependent hydrophobic recovery on plasma-treated superhydrophobic polypropylene using XPS and wettability measurements

In specific applications like ice-repellent coatings or membrane separation technology, wettability is a key parameter affecting the applicability of commodity polymers. This study presents a technique to fine-control the wetting properties of a hierarchically structured polypropylene surface, enabling the transition between superhydrophobic and superhydrophilic states. To demonstrate the tunability of the wetting properties of polypropylene (PP) substrate, we prepared in a consecutive way superhydrophobic (advancing contact angle (CAadv) of 152°) and superhydrophilic (CAadv of 0°) material by solvent-treatment and mild air plasma treatment. The optimal plasma treatment parameters to achieve superhydrophilic wetting behaviour, which is stable for at least one week of storage in air was also explored. Water contact angle measurement and X-ray photoelectron spectroscopy were used to monitor the time dependency of hydrophobic recovery on a hierarchically structured PP surface. With a simple model considering structural and wetting parameters, we characterized the droplet spreading behaviour of plasma-treated roughened surfaces, which exhibited superhydrophilic wetting behaviour with equilibrium CAadv of nearly 0°. The proposed model, which aligns well with experimental data, can be used to compare the droplet spreading behaviour of plasma-treated roughened surfaces.

Laser Direct Writing of Setaria Virids-Inspired Hierarchical Surface with TiO2 Coating for Anti-Sticking of Soft Tissue

In minimally invasive surgery, the tendency for human tissue to adhere to the electrosurgical scalpel can complicate procedures and elevate the risk of medical accidents. Consequently, the development of an electrosurgical scalpel with an anti-sticking coating is critically important. Drawing inspiration from nature, we identified that the leaves of Setaria Virids exhibit exceptional non-stick properties. Utilizing this natural surface texture as a model, we designed and fabricated a specialized anti-sticking surface for electrosurgical scalpels. Employing nanosecond laser direct writing ablation technology, we created a micro-nano textured surface on the high-frequency electrosurgical scalpel that mimics the structure found on Setaria Virids leaves. Subsequently, a TiO2 coating was deposited onto the ablated scalpel surface via magnetron sputtering, followed by plasma-induced hydrophobic modification and treatment with octadecyltrichlorosilane (OTS) to enhance the surface's affinity for silicone oil, thereby constructing a self-lubricating and anti-sticking surface. The spreading behavior of deionized water, absolute ethanol, and dimethyl silicone oil on this textured surface is investigated to confirm the effectiveness of the self-lubrication mechanism. Furthermore, the sticking force and quality are compared between the anti-sticking electrosurgical scalpel and a standard high-frequency electrosurgical scalpel to demonstrate the efficacy of the nanosecond laser-ablated micro-nano texture in preventing sticking. The findings indicate that the self-lubricating anti-sticking surface fabricated using this texture exhibits superior anti-sticking properties.

Superhydrophobic Composite Coatings Can Achieve Durability and Efficient Radiative Cooling of Energy-Saving Buildings

Passive daytime radiative cooling (PDRC) technology has received a great deal of attention in the field of energy efficiency and environmental protection as a sustainable technology and a large-scale and promising solution to mitigate the environmental impact of global warming. In this study, we prepared PDRC material by combining FEP with modified Al2O3 particles and using the method of spray combined with phase separation. The synergistic effect of the formed surface micronanostructures, combined with the molecular vibration of FEP and the phonon polarization resonance of Al2O3, further improves the optical performance of the PDRC coating. The PDRC coating has an average reflectivity of 0.96 in the solar spectral band (0.3-2.5 μm) and an average emissivity of 0.963 in the atmospheric window band ((8-13 μm). In addition, the PDRC coating had good hydrophobicity, and its water contact angle (WAC) reached 159.3°. Under direct sunlight conditions, PDRC materials have a good temperature drop (4.9 °C) compared to ambient temperatures and radiative cooling power (81.2 W/m2). The prepared coating maintains superhydrophobicity and excellent cooling performance when soaked in solutions of different pH values and UV radiation, which was of great significance for sustainable applications. Our work provides a form of long-term cooling that can be effectively implemented in green and energy-efficient buildings.

Functional Surfaces for Passive Fungal Proliferation Control: Effect of Surface Micro- and Nanotopography, Material, and Wetting Properties

Fungal proliferation can lead to adverse effects for human health, due to the production of pathogenic and allergenic toxins and also through the creation of fungal biofilms on sensitive surfaces (i.e., medical equipment). On top of that, food spoilage from fungal activity is a major issue, with food losses exceeding 30% annually. In this study, the effect of the surface micro- and nanotopography, material (aluminum, Al, and poly(methyl methacrylate), PMMA), and wettability against Aspergillus awamori is investigated. The fungal activity is monitored using dynamic conditions by immersing the surfaces inside fungal spore-containing suspensions and measuring the fungal biomass growth, while the surfaces with the optimum antifungal properties are also evaluated by placing them near spore suspensions of A. awamori on agar plates. Al- and PMMA-based superhydrophobic surfaces demonstrate a passive-like antifungal profile, and the fungal growth is significantly reduced (1.6-2.2 times lower biomass). On the other hand, superhydrophilic PMMA surfaces enhance fungal proliferation, resulting in a 2.6 times higher fungal total dry weight. In addition, superhydrophobic surfaces of both materials exhibit antifouling and antiadhesive properties, whereas both superhydrophobic surfaces also create an "inhibition" zone against the growth of A. awamori when tested on agar plates.

Green Synthesis of a Carbon Quantum Dots-Based Superhydrophobic Membrane for Efficient Oil/Water Separation

The efficient separation of oil and water is a significant challenge worldwide due to the increasing frequency of industrial oily wastewater. Previous work by our group utilizes biological metal-organic framework-based superhydrophobic (S.P) textile fabric for oil/water separation. However, this system is limited due to the low mechanical stability, so there is a need for producing a more robust S.P membrane for oil/water separation. In this study, we report on the synthesis of carbon quantum dots (CQD) from banana leaves via a hydrothermal process and their application in producing a robust S.P coating on textile fabric for oil/water separation. The CQDs were characterized using various techniques including TEM, XRD, absorbance spectroscopy, and the BET method. The TEM images showed that the CQDs were circular in shape with a size of 4.4 nm, while the XRD micrograph indicated that the CQDs were crystalline in nature. The UV-vis graph showed a peak at a wavelength of 278 nm, suggesting strong absorption in the ultraviolet region. The BET-specific surface area of the prepared CQDs is 845 m2/g, with a pore volume of 0.33 cm3/g, and a mean pore diameter of 1.62 nm. We examined the surface wettability, morphology, composition, oil absorption capacity, oil/water separation performance, flux rate, chemical stability, and mechanical stability of the S.P membrane. Our findings indicate that the developed CQD-based S.P membrane possesses excellent S.P properties, displaying high water contact angles of 163° and low water sliding angles of 1°. The membrane demonstrated superior oil absorption capacity, separation efficiency, and flux rate towards three different oils-petroleum ether, n-hexane, and silicone oil. Petroleum ether has the highest separation efficiency (99.5%), and flux rate (13,500 L m-2 h-1), while silicone oil has the lowest. However, silicone oil has the highest absorption capacity (218.9 g/g) and petroleum ether has the lowest (194.8 g/g). For the absorption capacity and separation efficiency, a one-way ANOVA test was conducted. The statistical analyses revealed significant differences in absorption capacity and separation efficiency for the three oils, highlighting the efficacy of the superhydrophobic membrane for tailored oil/water separation. Additionally, the S.P membrane exhibited good mechanical (the membrane maintains its superhydrophobicity until an abrasion length of 850 cm) and chemical stability (the membrane maintains its superhydrophobicity in pH range 1-13), withstanding abrasion and immersion in solutions of varying pH values. The CQD-based S.P membrane shows great potential as a promising material for oil/water separation applications, with excellent performance and stability under various environmental conditions.

Effect of Chemical Activation on Surface Properties of Poly(tetrafluoroethylene-co-hexafluoropropylene) Film

Due to their low surface energy, poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films must be treated by chemical or physical activation methods before using. Among these activation strategies, using sodium naphthalene solution is a popular one. However, the effect of this strategy’s chemical activation conditions on the surface properties of the FEP film is rarely discussed. In this study, FEP films were chemically activated by the sodium naphthalene solution with adjusting concentration, solvent, and activation time. With increasing concentration and activation time, many granular substances appeared on the surface of the FEP film. When tetrahydrofuran was used as a solvent, the color of the film gradually turned brown; when 1,3-dimethyl-2-imidazolidinone was chosen as the solvent, the color change was not very significant. The contact angle was significantly reduced from 112° before activation to 26° after activation, and the surface energy was greatly enhanced from 34 mN m−1 before activation to 66 mN m−1 after activation. In addition, compared with the FEP samples treated by Ar plasma, the sodium naphthalene system showed a stronger activation ability. Activated FEP films that suffered from the Ar plasma treatment could still maintain a higher energy surface than that of the pristine FEP.

A Review on Research Progress in Plasma-Controlled Superwetting Surface Structure and Properties

Superwetting surface can be divided into (super) hydrophilic surface and (super) hydrophobic surface. There are many methods to control superwetting surface, among which plasma technology is a safe and convenient one. This paper first summarizes the plasma technologies that control the surface superwettability, then analyzes the influencing factors from the micro point of view. After that, it focuses on the plasma modification methods that change the superwetting structure on the surface of different materials, and finally, it states the specific applications of the superwetting materials. In a word, the use of plasma technology to obtain a superwetting surface has a wide application prospect.