Low-pressure Plasma Technique Research Articles

Innovative Atmospheric Plasma Jets for Advanced Nanomaterial Processing

This study presents a comprehensive exploration of atmospheric pressure plasma jets (APPJs) as an innovative method for synthesizing and modifying nanomaterials, offering a versatile and efficient approach to tailoring their properties and functionalities. Unlike traditional low-pressure plasma techniques, APPJs operate at ambient conditions, providing significant advantages in scalability, cost-effectiveness, and environmental sustainability. This review delves into the recent advancements in APPJ technology, including the development of microfluidic configurations that enhance plasma generation and control, leading to improved efficiency, power, and user accessibility. These advancements have opened new possibilities in various fields, such as the development of antimicrobial coatings, advanced drug delivery systems, and high-performance solar cells. The ability of APPJs to facilitate precise surface engineering and targeted material deposition positions them as a transformative technology in nanomaterial processing. Despite their potential, challenges such as scalability and environmental impact must be addressed to realize widespread adoption. This study underscores the promise of APPJs in driving future industrial applications and highlights the need for continued innovation to overcome current limitations and unlock their full potential across multiple sectors.

Creating Nature-Inspired Surface Roughness and Modifying Surface Chemistry of PVDF Electrospun Fibers Using Low-Pressure Plasma towards Omniphobic Membrane for Long-term Distillation

Today, water scarcity as one of the world's most pressing challenges, has caused many concerns. Seawater desalination based on membrane distillation (MD) has been introduced as an effective solution to deal with this problem. The surface of membranes used in MD is required to be modified to guarantee long-term performance via creating resistance against membrane wetting by low surface tension feeds. In this regard, beetle skin-inspired roughness was created on the surface of poly(vinylidene fluoride) (PVDF) electrospun fibers using low-pressure plasma technique. Synergistically, 1H, 1H, 2H, 2H-perfluorooctyl acrylate (PFOA) was polymerized on the fiber surface to modify its chemistry. In other words, using the plasma polymerization technique, the membrane surface energy was reduced thanks to (1) the increase in membrane surface roughness and (2) the change in the membrane surface chemistry, as confirmed by field-emission scanning electron microscope (FESEM) imaging, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. These changes led to an omniphobic membrane repelling water, engine oil and isopropanol with contact angles of 150°, 135°, and 119°, respectively. The long-term performance of the developed omniphobic membrane was demonstrated by conducting air gap membrane distillation (AGMD) for a duration as long as 600 min using a feed solution containing 3.5 wt% NaCl and 0.6 mM sodium dodecyl sulfate (SDS), which is ten times better than the performance of pristine membrane (60 min). Overall, the surface modification technique considered in this work yields an omniphobic membrane with stable long-term performance without compromising the membrane flux and salt rejection.

Obtention of polymeric membrane fuel cells by low pressure plasma technique: Evaluation of total cell efficiency by function on the amount of platinum and the thickness of the deposited carbon support

This work aimed to obtain catalytic support over polymeric membrane building a fuel cell using low pressure plasma technique. For this, polymeric membranes were coated with carbon layer and platinum nanoparticles. The procedures were performed in separate steps in order to obtain firstly carbon layer and catalytic platinum nanoparticles. In the first step, the plasma processes were carried methane in order to obtain carbon layer over the polymeric membrane. At this stage, in order to obtain different thicknesses, were made several processes, reaching a thickness of 0,36pm to 1,4pm. The second step was to get the platinum nanoparticles on the carbon layer. For this, was used a platinum solid source and argon plasma. The study relied primarily on assessing the influence of the carbon layer on the performance of fuel cell. Compared with the commercial processes, it was observed that the results for fuel cells obtained by plasma have a better electric contact on three cell layers (catalyst - electrolyte - reagent). By electrochemical activity test was possible observe increase of reverse voltage of 0.8 volts to 1.24 volts according to increase the thickness of the carbon layer. The same behavior was also observed in the analysis of total efficiency, which was limited to 50% of maximum efficiency of commercial cell due the thickness of the carbon layer deposited during the preparation of this study, indicating a greater thickness with carbon it is possible to achieve the same efficiency of cells better than commercial.

Low-pressure plasma enhanced immobilization of chitosan on low-density polyethylene for bio-medical applications

With the aim of improving blood compatibility of low density polyethylene (LDPE) films, an effective low-pressure plasma technology was employed to functionalize the LDPE film surfaces through in-situ grafting of acrylic acid (AAc). Subsequently, the molecules of poly(ethylene glycol) (PEG) and chitosan (CHI) were immobilized on the surface of grafted LDPE films. The unmodified and modified LDPE films were analyzed using various characterization techniques such as contact angle, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray photo electron spectroscopy (XPS) to understand the changes in surface properties such as hydrophilicity, surface topography and chemical composition, respectively. Furthermore, LDPE films have been subjected to an ageing process to determine the durability of the plasma assisted surface modification. The blood compatibility of the surface modified LDPE films was confirmed by in vitro tests. It was found that surface modified LDPE films show better hydrophilic behavior compared with the unmodified one. FTIR and XPS results confirm the successful immobilization of CHI on the surface of LDPE films. LDPE films showed marked morphological changes after grafting of AAc, PEG and CHI which were confirmed through AFM imaging. The in vitro blood compatibility tests have clearly demonstrated that CHI immobilized LDPE films exhibit remarkable anti thrombogenic nature compared with other modified films. Surface modified LDPE films through low-pressure plasma technique could be adequate for biomedical implants such as artificial skin substrates, urethral catheters or cardiac stents, among others.

Plasma Surface Modification of Commercial SBS Rubbers for Enhanced Adhesive Bonding

An attempt to replace a wet chemical surface modification of styrene-butadiene elastomers (SBS), improving their adhesion to polyurethane dispersion adhesives, with a clean low-pressure plasma technique was undertaken. Investigations were performed on commercial SBS rubbers. The plasma was generated by an RF discharge (13.56 MHz, plate electrode reactor) in pure argon (Ar). The rubbers surfaces were investigated by 180°-peel tests and scanning electron microscopy (SEM). The presented results indicate that the plasma treatment is a very promising method of improving the adhesion properties of commercial SBS rubbers elastomers and it should replace the wet chemical methods in industry.DOI: http://dx.doi.org/10.5755/j01.ms.18.2.1914

Sterilization of Heat-Sensitive Silicone Implant Material by Low-Pressure Gas Plasma

In recent years, plasma treatment of medical devices and implant materials has gained more and more acceptance. Inactivation of microorganisms by exposure to ultraviolet (UV) radiation produced by plasma discharges and sterilization of medical implants and instruments is one possible application of this technique. The aim of this study was to evaluate the effectiveness of this sterilization technique on silicone implant material. Bacillus atrophaeus spores (10(6) colony-forming units [CFUs]) were sprayed on the surfaces of 12 silicone implant material samples. Four plasma sets with different gas mixtures (argon [Ar], argon-oxygen [Ar:O(2)], argon-hydrogen [Ar:H(2)] and argon-nitrogen [Ar:N(2)]) were tested for their antimicrobial properties. Post-sterilization mechanical testing of the implant material was performed in order to evaluate possible plasma-induced structural damage. The inductively coupled low-pressure plasma technique can achieve fast and efficient sterilization of silicone implant material without adverse materials effects. All four gas mixtures led to a significant spore reduction, and no structural damage to the implant material could be observed.

Doppelt induktiv gekoppeltes Niederdruckplasma zur Sterilisation von medizinischen Implantatmaterialien / A double inductively coupled low-pressure plasma for sterilization of medical implant materials

The potential of plasma treatment in medicine is only slowly gaining acceptance. Inactivation of germs through exposure to UV radiation produced by plasma discharges and sterilization of medical implant devices and instruments is one possible application of this technique. In addition, due to the manifold possibilities of coating through plasma processes, quick sterilization-coating combinations of medical implant devices are possible. To analyze the effectiveness of this sterilization process on different material surfaces, three different alloys (X2CrNiMo18-15-3, Ti6Al7Nb and Ti6Al4V) and one thermoplastic material (ultra-high molecular weight polyethylene, UHMWPE), commonly used in medical implant devices, were examined in the presented study. After spraying Bacillus atrophaeus spores (10(6) CFU) on the surfaces of four different implant materials tested in this study (X2CrNiMo18-15-3, UHMWPE, Ti6Al7Nb and Ti6Al4V), it was demonstrated in each of four gas mixtures used (Ar, Ar:O2, Ar:H2 and Ar:N2) that due to the application of inductively coupled low-pressure plasma technique, plain medical implant materials can be sterilized rapidly, and can be protective and efficient.

Chondrogenic Differentiation of Human Articular Chondrocytes Differs in Biodegradable PGA/PLA Scaffolds

Cartilage tissue engineering is applied clinically to cover and regenerate articular cartilage defects. Two bioresorbable nonwoven scaffolds, polyglycolic acid (PGA) and poly(lactic-co-glycolic acid) (PLGA) (90/10 copolymer of L-lactide and glycolide), were seeded with human chondrocytes after initial progeny in a monolayer with a serum-free medium. Two subgroups of nontreated and plasma-treated (using low-pressure plasma technique) scaffolds were investigated. The constructs were cultivated after seeding in six-well plates with serum-free medium for 7 days and implanted subcutaneously into nude mice for 6 and 12 weeks. Chondrogenic differentiations were investigated using immunhistology and reverse transcriptase-polymerase chain reaction. Cell adhesion only differed from 50% to 65% without a significant difference between the groups. During further cultivation for 7 days, the aggrecan synthesis of the seeded constructs was always higher in the PGA groups (p < 0.05). The mRNA gene expression for collagen type II was significantly higher in the PGA groups after 6 and 12 weeks (p < 0.05). A decrease in the expression of collagen type I was investigated in all groups. The expression for collagen type X and cartilage oligomeric matrix protein (COMP) increased in all groups over time. After cell proliferation in serum-free medium, the long-term chondrogenic differentiation in PGA scaffolds in vitro is cartilage specific and may be utilized in cartilage tissue engineering applications.

Plasma-induced graft-polymerization of flame retardant monomers onto PAN fabrics

This paper presents the use of the low-pressure plasma technique to confer a fire-resistant character to polyacrylonitrile (PAN) textiles. We investigated the argon plasma-induced graft-polymerization of four acrylate monomers containing phosphorus, diethyl(acryloyloxyethyl)phosphate (DEAEP), diethyl-2-(methacryloyloxyethyl)phosphate (DEMEP), diethyl(acryloyloxymethyl) phosphonate (DEAMP) and dimethyl(acryloyloxymethyl)phosphonate (DMAMP), which are known to be effective monomers for the fireproofing of polymeric substrates in classical polymerizations. The grafting and the polymerization processes taking place on the surface of the PAN textile were followed by weighing measurements, IR(ATR) spectroscopy and SEM. The fire retardant character of the treated fabrics was investigated by thermogravimetric analyses and LOI measurements. Furthermore, we were able to prove the persistence of the coatings towards several washing cycles by using the accelerated method of laundering proposed by McSherry and al.

Polymerization and surface modification by low pressure plasma technique

A durable water repellent, stain resistant or flame retardant character can be conferred to polyacrylonitrile (PAN) textiles by using the plasma induced graft polymerization technique. The monomers used are perfluoroalkylacrylate, (meth)acrylate phosphates, and phosphonates which are well known to be effective for the waterproofing and the fireproofing of polymeric substrates, respectively.

Current trends in biomaterial surface functionalization—nitrogen-containing plasma assisted processes with enhanced selectivity

Low-pressure gas-discharge plasmas are widely used for polymer surface functionalization on industrial scale. For biomaterial applications, the density and selectivity of the functionalization are of particular importance, because functional groups control the immobilization of biomolecules. Therefore, surface modification of biomaterials is a challenging task for low-pressure plasma technique. Plasma processes have been successfully applied to various polymer types in order to generate multifunctional surfaces. This paper discusses the present state and the prospects of non-coating plasma processes to generate mono functional surfaces of controlled amino group density. Such surfaces appear most desirable for many applications. The results of various microwave- and radio-frequency- excited plasma processes reported in the literature are reviewed and compared to a sequence of experiments that was conducted in a UHV reaction environment. Non-thermal plasmas are especially well suited for thermally damageable polymers. The effect of hydrogen admixture to discharges in nitrogen and ammonia is discussed in detail. The optimization of process parameters lead to highly selective amino functionalization of high density. The selectivity reached 100% -NH 2/N at a surface density of amino groups of 3% -NH 2/C.

Friction and wear characteristics of aluminum bronze coatings on steel substrates sprayed by a low pressure plasma technique

In the present research work, the tribological characteristics of low pressure plasma sprayed aluminum bronze coatings against steel ball (SUJ2), have been studied. The effects of different loads, as well as high speed and boundary lubrication conditions, have been examined using the sliding tester. The films were synthesized using a low-pressure plasma spraying technique under different operating conditions. The correlation between the processing variables and the tribological characteristics of the resulting aluminum bronze coatings has been studied. Optical and scanning electron microscopy was employed to evaluate the morphology of the coating’s microstructures. The depths of the wear tracks were evaluated using surface texture instrument. The results indicate that under optimum operating conditions, the test samples exhibit a dense microstructure with a high hardness, low coefficient of friction and high wear resistance. Moreover, the strength of the interface between the film and the substrate was found to be adequate for many industrial applications. The range of optimum operating conditions has also been identified.

PLASMA-LIQUID TECHNOLOGIES FOR TREATMENT OF ARCHAELOGICAL ARTIFACTS

Plasma-liquid technologies at atmospheric pressure provide a wide range of possibilities for applications. One of them, the treatment of archaeological artifacts, is presented in this paper. The effects of discharges between a metal electrode and a solution surface and/or an interaction of hollow cathode plasma jet, plasma pencil, with liquid on the corroded surface of bronze and glass artifacts were studied. It was compared with standard low pressure plasma techniques and with the effects of electrolysis. Original and treated objects were characterized by means of scanning electron microscope (SEM) with energy dispersive analyser used for the spot elemental analyses.

Plasma treatments and plasma deposition of polymers for biomedical applications

The aim of this review is to describe how biomaterial engineering processes, particularly in the field of polymer modifications for enhanced blood-compatibility, can take advantage of low-pressure plasma techniques. It will also be emphasized how a diagnostic approach on both plasma and surface reactions can lead to understand and control the chemistry of plasma processes.

Characteristics and corrosion performance of 80Ni-20Cr coating deposited by on-site thermal spraying

New controlled atmosphere on-site spraying systems were developed to deposit a high-quality coating with superior resistance to wet corrosion. Characteristics and corrosion resistance of coatings deposited by arc and flame spraying of wire in argon gas were compared with those of coatings deposited by conventional and low-pressure plasma techniques. It was found that the coating deposited by the arc spraying of wire in argon gas is free of oxides and possesses excellent corrosion resistance in chloride and acid solutions. The coating suffers slight pitting and crevice corrosion associated with the isolated pores and electric potential paths. Corrosion resistance was improved by using a modified spraying system.

Glow discharge characteristics of importance in low pressure plasma techniques : L Holland,Unit for Plasma Materials Processings, University of Sussex, Brighton BN1 9QH, UK

Glow discharge characteristics of importance in low pressure plasma techniques : L Holland,Unit for Plasma Materials Processings, University of Sussex, Brighton BN1 9QH, UK

Thin water vapor barriers for paper

AbstractLow‐pressure plasma technique was used in the deposition of thin polymeric coatings upon a filter paper. Sixteen different monomers, including aromatic and aliphatic hydrocarbons, nitriles, chlorine‐containing compounds, and a silane, were used in the coatings. Most of the coatings functioned as water vapor barriers in different degrees, and the coated samples possessed wet tensile strengths anywhere from 3 to 34 times that of the untreated samples. Attenuated total reflectance infrared spectroscopy was used to study the chemical structure of the coatings.