Investigating the Behavior of Thin-Film Formation over Time as a Function of Precursor Concentration and Gas Residence Time in Nitrogen Dielectric Barrier Discharge.

This study aims to establish a correlation between the fragmentation process and the growth mechanisms of a coating deposited on a fluoropolymer. Deposition was carried out using dielectric barrier discharge at atmospheric pressure, employing an oxygen-containing organic precursor in a nitrogen environment. The findings reveal that the impact of precursor concentration on the formation of specific functionalities is more significant than the influence of treatment time. The X-ray photoelectron spectroscopy (XPS) results obtained indicate a reduction in the N/O ratio on the coating's surface as the precursor concentration in the discharge increases. Fourier transform infrared spectroscopy (FTIR) analysis, conducted in the spectral range of 1500 cm-1 to 1800 cm-1, confirmed the connection between the chemical properties of plasma-deposited thin films and the concentration of organic precursors in the discharge. Furthermore, the emergence of nitrile moieties (C≡N) in the FTIR spectrum at 2160 cm-1 was noted under specific experimental conditions.

Surface Modification of Flax Fibers with TMCTS-Based PECVD for Improved Thermo-Mechanical Properties of PLA/Flax Fiber Composites.

Significant progress has been made in recent years in the use of atmospheric pressure plasma techniques for surface modification. This research focused on the beneficial effects of these processes on natural by-products, specifically those involving natural fiber-based materials. The study explored the deposition of hydrophobic organosilicon-like thin films onto flax fibres through plasma-enhanced chemical vapour deposition (PECVD), using tetramethylcyclotetrasiloxane (TMCTS) as the precursor. After the successful deposition of hydrophobic organosilicon-like thin films onto the flax fibres, polylactic acid (PLA) composite materials were fabricated. This fabrication process sets the stage for an in-depth analysis of the modified materials. Subsequently, these flax fabrics were subjected to meticulous characterization through scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results demonstrated successful TMCTS deposition on the surface which led to a complete hydrophobization of the flax fibers. Mechanical tests of the PLA/flax fibre composites revealed a significant improvement in load transfer and interfacial compatibility following the surface modification of the flax fibres. This improvement was attributed to the enhanced adhesion between the modified fibres and the PLA matrix. The findings highlight the potential of TMCTS-based PECVD as a practical surface modification technique, effectively enhancing the mechanical properties of PLA/flax fibre composites. These developments open exciting possibilities for sustainable and high-performance composite materials in various industries.

Fragmentation Mechanism in a Nitrogen Dielectric Barrier Discharge Plasma on Fluoropolymer Polymer Films.

Due to their chemical inertness and low friction coefficient, fluoropolymers are today widely employed in sectors of activity as diverse and distinct as the textile industry, architectural sector, and medicine. However, their low surface energy results in poor adhesion, for example, when used for a component in a composite device with multiple other materials. Among the techniques used to enhance their adhesion, atmospheric pressure discharges provide a fast and low-cost method with a reduced environmental impact. Although this approach has proven to be efficient, the different chemical and physical processes in the discharge remain not fully understood. In this study, fluoropolymer surfaces were modified using an atmospheric pressure dielectric barrier discharge in a nitrogen and organic precursor environment. To prevent any damage to fluoropolymer surfaces, the dissipated power in the discharges was tuned by applying a duty cycle. Evidence shows that plasma treatment allows for the incorporation of oxygen and nitrogen in the surface resulting in the formation of hydrophilic functionalities such as carbonyl groups both in ketone and amide form, amine, and hydroxyl groups after 180 s of treatment. Overall, the data reveal that the discharge duty cycle has more effect on the oxygen and carbon content in the coating than the precursor concentration. In addition, increasing the precursor concentration limits the molecular fragmentation and nitrogen incorporation into the coating. These experiments enable the building of a better fundamental understanding of the formation mechanism of such chemical moieties at the fluoropolymer surface.

Erratum: Profili et al. Overview of the User Experience for Snorkeling Mask Designs during the COVID-19 Pandemic. Healthcare 2021, 9, 204.

The authors would like to make the following corrections to the published paper [...].

Overview of the User Experience for Snorkeling Mask Designs during the COVID-19 Pandemic.

During the first wave of the COVID-19 pandemic, industries and academic institutes have collaborated to resolve the worldwide medical supply shortage issues. Innovative designs of 3D-printed items were proposed and developed by the maker community as a temporary solution to address the lack of personal protective equipment. An overview of global ongoing and past initiatives during the COVID-19 pandemic along with their challenges on retrofitting full-face snorkeling masks for healthcare applications such as splash-proof face shields, respirator masks and non-invasive ventilation systems are reported in this contribution. This study reviews these global initiatives and challenges. From our analysis, the present situation highlights the need to build solid networks between healthcare institutes and the different rapid prototyping initiatives. A clear feedback system needs to be implemented to facilitate effective collaboration between engineering (maker) and healthcare teams, to optimize the available human resources, and to achieve adequate product developments responding to the needs of healthcare workers.

Use of 3D printed connectors to redesign full face snorkeling masks in the COVID-19 era: A preliminary technical case-study.

The COVID-19 pandemic resulted in severe shortages of personal protection equipment and non-invasive ventilation devices. As traditional supply chains could not meet up with the demand, makeshift solutions were developed and locally manufactured by rapid prototyping networks. Among the different global initiatives, retrofitting of full-face snorkeling masks for Non-Invasive-Ventilation (NIV) applications seems the most challenging. This article provides a systematic overview of rapid prototyped - 3D printed - designs that enable attachment of medical equipment to snorkeling masks, highlighting potential and challenges in additive manufacturing. The different NIV connector designs are compared on low-cost 3D fabrication time and costs, which allows a rapid assessment of developed connectors for health care workers in urgent need of retrofitting snorkeling masks for NIV purposes. Challenges and safety issues of the rapid prototyping approach for healthcare applications during the pandemic are discussed as well. When critical parameters such as the final product cost, geographical availability of the feedstock and the 3D printers and the medical efficiency of the rapid prototyped products are well considered before deploying decentralized 3D printing as manufacturing method, this rapid prototyping strategy contributed to reduce personal protective equipment and NIV shortages during the first wave of the COVID-19 pandemic. It is also concluded that it is crucial to carefully optimize material and printer parameter settings to realize best fitting and airtight connector-mask connections, which is heavily depending on the chosen feedstock and type of printer.

Development of Organosilicon-Based Superhydrophobic Coatings through Atmospheric Pressure Plasma Polymerization of HMDSO in Nitrogen Plasma.

Water-repellent surfaces, often referred to as superhydrophobic surfaces, have found numerous potential applications in several industries. However, the synthesis of stable superhydrophobic surfaces through economical and practical processes remains a challenge. In the present work, we report on the development of an organosilicon-based superhydrophobic coating using an atmospheric-pressure plasma jet with an emphasis on precursor fragmentation dynamics as a function of power and precursor flow rate. The plasma jet is initially modified with a quartz tube to limit the diffusion of oxygen from the ambient air into the discharge zone. Then, superhydrophobic coatings are developed on a pre-treated microporous aluminum-6061 substrate through plasma polymerization of HMDSO in the confined atmospheric pressure plasma jet operating in nitrogen plasma. All surfaces presented here are superhydrophobic with a static contact angle higher than 150° and contact angle hysteresis lower than 6°. It is shown that increasing the plasma power leads to a higher oxide content in the coating, which can be correlated to higher precursor fragmentation, thus reducing the hydrophobic behavior of the surface. Furthermore, increasing the precursor flow rate led to higher deposition and lower precursor fragmentation, leading to a more organic coating compared to other cases.