Low-pressure Plasma Treatment Research Articles

Improved Adhesion of Bacterial Cellulose on Plasma-Treated Cotton Fabric for Development of All-Cellulose Biocomposites.

Cellulose produced by bacteria (BC) is considered a promising material for the textile industry, but the fragile and sensitive nature of BC membranes limits their broad applicability. Production of all-cellulose biocomposites, in which the BC is cultivated in situ on a cotton fabric, could solve this problem, but here a new issue arises, namely poor adhesion. To overcome this challenge, cotton fabric was modified with low-pressure oxygen plasma in either afterglow, E-mode, or H-mode. All-cellulose biocomposites were prepared in situ by placing the samples of cotton fabric in BC culture medium and incubating for 7 days to allow BC microfibril networks to form on the fabric. Modification of cotton fabric with oxygen plasma afterglow led to additional functionalization with polar groups, and modification with oxygen plasma in H-mode led also to etching and surface roughening of the cotton fibers, which improved the adhesion within the biocomposite. In addition, these biocomposites showed higher deformation capacities. Modification of the cotton fabric over a longer period in E-mode was found to be unsuitable, as this caused strong etching, which led to the defibrillation of cotton fibers and poor adhesion of BC. This study highlights the potential of low-pressure plasma treatment as an environmentally friendly method to improve the performance of cellulose-based biocomposites.

Diamond Surfaces with Lateral Gradients for Systematic Optimization of Surface Chemistry for Relaxometry - a Low-Pressure Plasma-Based Approach.

Diamond is increasingly popular because of its unique material properties. Diamond defects called nitrogen vacancy (NV) centers allow for measurements with unprecedented sensitivity. However, to achieve ideal sensing performance, NV centers need to be within nanometers from the surface and are thus strongly dependent on the local surface chemistry. Several attempts have been made to compare diamond surfaces. However, due to the high price of diamond crystals with shallow NV centers, a limited number of chemical modifications have been studied. Here, we developed a systematic method to investigate the continuity of different local environments with varying densities and natures of surface groups in a single experiment on a single diamond plate. To achieve this goal, we used diamonds with a shallow ensemble of NV centers and introduced a chemical gradient across the surface. More specifically, we used air and hydrogen plasma. The gradients were formed by a low-pressure plasma treatment after masking with a right-angled triangular prism shield. As a result, the surface contained gradually more oxygen/hydrogen toward the open end of the shield. We then performed wide-field relaxometry to determine the effect of surface chemistry on the sensing performance. As expected, relaxation times and thus sensing performance indeed vary along the gradient.

Development of surface-activated La0.6Ca0.4MnO3 perovskite-type electrodes using oxygen plasma for highly stable supercapacitor application

This study introduces a novel and efficient approach for synthesizing perovskite-type nanoparticles and advanced plasma surface activation to significantly improve the supercapacitor's performance. High-purity La0.6Ca0.4MnO3 (LCMO) perovskite nanoparticles with a crystalline structure were synthesized using a facile coprecipitation technique, followed by an innovative low-pressure DC glow-discharge plasma treatment in an oxygen atmosphere. This plasma surface activation process enhances the surface properties of the nanoparticles and boosts their electrochemical performance, representing a transformative modification method for energy storage materials. Detailed analysis of the synthesized and surface-activated LCMO (SA@LCMO) nanoparticles revealed a well-defined cubic morphology with a remarkable surface area of 95 m2/g, as confirmed by TEM and BET analysis. The plasma-treated SA@LCMO electrodes demonstrated superior supercapacitor performance, delivering an impressive specific capacitance of 453 F/g at a current density of 1 A/g more than doubling the 225.8 F/g achieved by untreated LCMO electrodes. Additionally, the SA@LCMO electrodes exhibited exceptional cycle stability, retaining 87 % of their capacitance and achieving a coulombic efficiency of 95.2 % after 10,000 GCD cycles. The material also showed promising energy storage capabilities, with a maximum energy density of 3.92 Wh/kg at a power density of 170.6 W/kg. These results highlight the transformative impact of plasma surface activation on perovskite nanomaterials, positioning the SA@LCMO as a highly promising candidate for next-generation energy storage technologies with superior energy density, durability, and performance. This study introduces new avenues for surface engineering perovskite-based materials to create scalable high-performance energy storage devices.

Study of the Gelatinization, Fatty Acid Profiles and the Conversion of Ergosterol into Vitamin D in Wheat Shorts by Optimization of Low-pressure Radiofrequency Cold Plasma Treatment Conditions

Study of the Gelatinization, Fatty Acid Profiles and the Conversion of Ergosterol into Vitamin D in Wheat Shorts by Optimization of Low-pressure Radiofrequency Cold Plasma Treatment Conditions

Plasma Technology Applied to Improve Wettability for Emerging Mycelium-Based Materials

Plasma technology is increasing its applications in the textile industry for conferring surface functionalities through greener processes. In this study, plasma treatments are studied to improve the wettability of mycelium-based material, an emerging material with a lot of potential in the near future. The plasma effect was characterized by assessing the added functionality (wettability) and inspecting surface modifications with different techniques, such as scanning electron microscopy (SEM) and X-Ray photoelectron spectroscopy (XPS). Low pressure plasma (LPP) treatments were successfully applied into the mycelium-based material and optimal power of discharge and treatment time were set for this material (750 W, 17.5 min). With the optimized LPP treatments, the water absorption capacity of mycelium-based material was improved by 2000% and some surface morphological modifications were observed by SEM analysis. On the other hand, XPS analysis demonstrated how the plasma treatment changes the surface composition.

Effects of cold plasma treatment on the biological performances of decellularized bovine pericardium extracellular matrix-based films for biomedical applications

Aim: Since decades, decellularized extracellular matrix (dECM)-derived materials have received worldwide attention as promising biomaterials for tissue engineering and biomedical applications. Soluble dECM is a versatile raw material that can be easily engineered into the desired shapes and structures. However, there are still some limitations restricting its use, including low hydrophilicity and smooth surfaces, which negatively influence cell adhesion/spreading. The objective of the present study was to investigate surface modification by nitrogen/hydrogen (N2/H2) low-pressure cold plasma treatment as a potential technique to improve the biological response of bovine pericardium dECM films. Methods: Bovine pericardium dECM was enzymatically digested and lyophilized prior to the preparation of thin films via solvent-casting method. Changes in surface properties after plasma treatment were investigated using water contact angle (WCA) and X-ray photoelectron spectroscopy (XPS) measurements. Immunofluorescence staining and resazurin assay for human dermal fibroblasts (HDFs) cultured on the dECM films were used to assess the bioactivity of dECM films. Finally, the hemocompatibility of the films was investigated via clotting time and hemolysis assay. Results: WCA and XPS results revealed that oxygen (O)- and N-containing functional groups were incorporated onto the film surface and an increase in hydrophilicity was observed after plasma treatment. In vitro experiments showed that cell adhesion in plasma-treated dECM films is much faster if compared to the untreated controls. Moreover, the fibroblast proliferation increased after plasma surface modifications. Finally, the hemocompatibility analysis results indicated a delayed blood clotting and no hemolytic effects for all the tested samples. Conclusions: These findings confirmed the potential of dECM as raw material for biocompatible thin films fabrication. Additionally, plasma surface treatment emerged as an eco-friendly and cost-effective strategy to enhance in vitro cell attachment and proliferation on dECM films, expanding their applications in biomedicine.

Adsorption Layer Properties and Foam Behavior of Aqueous Solutions of Whey Protein Isolate (WPI) Modified by Vacuum Cold Plasma (VCP)

For years, cold plasma processing has been used as a non-thermal technology in industries such as food. As interfacial properties of protein play a remarkable role in many processes, this study investigates the effect of cold plasma on the foaming and interfacial behavior of WPI. The objective of this study is to evaluate the effect of different gases (air, 1:1 argon–air mixture, and sulfur hexafluoride (SF6)) used in low-pressure cold plasma (VCP) treatments of whey protein isolate (WPI) on the surface and foaming behavior of aqueous WPI solutions. Dynamic surface dilational elasticity, surface tension isotherms, surface layer thickness, and the foamability and foam stability were investigated in this study. VCP treatment did not significantly affect the adsorption layer thickness. However, an increase in induction time, surface pressure equilibrium value, and aggregated size is observed after SF6VCP treatment, which can be attributed to the reaction of WPI with the reactive SF6 species of the cold plasma. The surface dilational elastic modulus increased after VCP treatment, which can be related to the increased mechanical strength of the protein layer via sulfonation and aggregate formation. VCP treatment of WPI increases the foam stability, while the average diameter of foam bubbles and liquid drainage in the foam depends on the gas used for the cold plasma.

Effect of Intermittent Low-Pressure Radiofrequency Helium Cold Plasma Treatments on Rice Gelatinization, Fatty Acid, and Hygroscopicity.

To establish the safe and reproducible effects of cold plasma (CP) technology on food products, this study evaluated the gelatinization parameters, fatty acid profile, and hygroscopic properties of rice grains repeatedly treated with low-pressure radiofrequency (RF) helium CP (13.56 MHz, 140 Pa, 120 W-20s, 0-4 times, and 300 g sample). Compared with the untreated (zero times) sample, with an increase in CP treatment times from one to four on rice, the water contact angle and cooking time decreased, while the water absorption rate and freshness index increased, and the pH value remained unchanged. CP repeating treatments essentially had no effect on the gelatinization enthalpy, but significantly increased the peak temperature of gelatinization. From the pasting profile of rice that has been repeatedly CP treated, the peak, breakdown, and setback viscosities in flour paste decreased. CP repeating treatments on rice did not change the short-range molecular order of starch. Compared with the untreated sample, the first helium CP treatment maintained the content of C18:1n9c, C18:2n6c, and C18:3n3, but the second to fourth CP treatment significantly decreased contents of these fatty acids (FAs) as the C18:0 content increased. The first three CP treatments can increase the water and sucrose solvent retention capacity in rice flours. CP repeatedly treated rice first exhibits the similar monolayer water content and solid surface area of water sorption. Principal component analysis shows that contact angle, pasting parameters, and fatty acid profile in milled rice are quite sensitive to CP treatment. Results support that the effect of low-pressure RF 120W helium CP treatment 20 s on rice grains is perdurable, and the improvement of CP intermittent treatments on rice cooking and pasting properties is an added benefit, and the hygroscopic properties of rice was kept.

Effect of low-pressure plasma treatment on the thermal behaviour of organo-modified montmorillonite nanoclay

The thermal behaviour of nanoclay can be considered an important factor in obtaining high-performance polymer nanocomposite. Thus, the current study aims to investigate the effect of plasma treatment on the thermal stability of two organically modified nanoclays, Cloisite 30B (C30B) and Nanomer I.34TCN (I.34TCN), compared with pristine NaMMT.The nanoclays were studied and characterised using Thermogravimetric Analysis (TGA). TGA was used to measure the weight loss of the plasma-treated and untreated nanoclays (C30B, I.34TCN, and NaMMT nanoclays) over a 30-630 C temperature range.Based on TGA results, the decomposition of all plasma-treated nano clays (C30B, I.34TCN and pristine NaMMT) was shifted to a lower temperature than in the untreated ones at all those stages. Thus, plasma treatment was successfully used as a convenient method to alter the chemical structure and surface morphology of MMT nanoclays for better thermal behaviour and filling distribution.This hypothesis can be corroborated by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) for a better understanding of the structural and surface changes that occurred due to the plasma action, which can provide an interpretation of the changes in the thermal behaviour of nanoclays.The plasma treatment, therefore, can improve the thermal stabilisation of the nanocomposite powders for the LS fabricated parts and even for the surrounding powder for the recovery process. Plasma-treated nano clay, therefore, can be used to reinforce polymers with an expectation of increasing the thermal stability of the resultant composites. Thus, the plasma-treated composite can be fabricated for laser sintering applications in fields that require high thermal stability.The surface modification of nanoclay powders via plasma treatment can be used as a convenient method to alter the chemical structure and surface morphology for better thermal behaviour and filling distribution.

The Influence of Low-Pressure Plasma Treatments on the Lap Shear Strength of Laser-Joined AISI 304 Hybrids with Polypropylene and Polyamide 6.6

This paper investigates if the polar groups induced by a plasma treatment can increase the lap shear strength of laser-joined metal and plastic hybrids. Optimal laser joining parameters for cold-rolled AISI304–polyamide 6.6 and sandblasted AISI304–polypropylene hybrids were developed at 2.85 MPa and 4.22 MPa, respectively. The surface free energy was doubled for all used plasma gases to a value of ca. 80 mN m−1 at 180 s. The plasma-treated samples were joined and tested. The arithmetic means of the plasma-treated hybrids’ lap shear strength with polyamide 6.6 varied slightly, but all measured values were within the range of the untreated samples. Residue on the sheared metal samples indicated covalent bonds between AISI304 and polyamide 6.6. The lap shear strengths of the plasma-treated polypropylene hybrids were significantly reduced between −30.8% and −53.3%, depending on the used plasma gas. This was attributed to the over-aging and development of low-molecular-weight oxidized materials, which led to a weak boundary layer. No residue of polypropylene was found on treated or untreated lap shear samples. No correlation between the surface free energy and lap shear strength could be found.

The Preparation of Silver and Gold Nanoparticles in Hyaluronic Acid and the Influence of Low-Pressure Plasma Treatment on Their Physicochemical and Microbiological Properties.

Nanometals constitute a rapidly growing area of research within nanotechnology. Nanosilver and nanogold exhibit significant antimicrobial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anticancer properties. The size and shape of nanoparticles are critical for determining their antimicrobial activity. In this study, silver and gold nanoparticles were synthesized within a hyaluronic acid matrix utilizing distilled water and distilled water treated with low-pressure, low-temperature glow plasma in an environment of air and argon. Electron microscopy, UV-Vis and FTIR spectra, water, and mechanical measurements were conducted to investigate the properties of nanometallic composites. This study also examined their microbiological properties. This study demonstrated that the properties of the composites differed depending on the preparation conditions, encompassing physicochemical and microbiological properties. The application of plasma-treated water under both air and argon had a significant effect on the size and distribution of nanometals. Silver nanoparticles were obtained between the range of 5 to 25 nm, while gold nanoparticles varied between 10 to 35 nm. The results indicate that the conditions under which silver and gold nanoparticles are produced have a significant effect on their mechanical and antibacterial properties.

Oxygen plasma treated thermoplastics as integrated electroresponsive sensors

Polypropylene (PP), thermoplastic polyurethane (TPU), polyethylene terephthalate glycol (PETG) and polylactic acid (PLA) 3D printed specimens, which are intrinsically non-electroresponsive materials, have been converted into electroresponsive electrodes applying a low-pressure oxygen plasma treatment. After complete chemical, morphological and electrochemical characterization, plasma treated samples have been applied as integrated electrochemical sensors for detecting dopamine and serotonin by cyclic voltammetry and chronoamperometry. Results show differences in the sensing behavior, which have been explained on the basis of the chemical structure of the pristine materials. While plasma treated PLA exhibits the highest performance as electrochemical sensor in terms of sensitivity (lowest limits of detection and quantification) and selectivity (against uric acid and ascorbic acid as interfering substances), plasma treated PP displays the poorest behavior due to its low polarity compared to PLA 3D-printed electrodes. Instead, plasma treated TPU and PETG shows a very good response, much closer to PLA, as sensitive electrodes towards neurotransmitter molecules (dopamine and serotonin). Overall, results open a new door for the fabrication of electrochemical conductive sensors using intrinsically insulating materials, without the need of chemical functionalization processes.

Comparative analysis of primers and alternative polypropylene pre-treatment techniques

ABSTRACT The test polypropylene substrates obtained from the original plastic car parts for Škoda Superb were subjected to 10 pre-treatment techniques: solvent cleaning (isopropanol, xylene), mechanical abrasion, immersion in a chromic acid mixture, flame activation, atmospheric and low-pressure plasma treatment, corona discharges and the application of two different primers (also called adhesion promoters). One of the primers, based on chlorinated polypropylene, was commercially available, while the other was prepared in our laboratory using polypropylene grafted with maleic anhydride. The test substrates were characterized using contact angle measurement for designation of surface free energy, Atomic Force Microscope (AFM) for roughness analysis, Scanning Electron Microscopy (SEM) for surface topography, and Energy Dispersive X-ray Spectrometry (EDX) for surface oxygen and contamination analysis. The suitability of the surface preparation methods in the industry was evaluated through peel strength tests (adhesive bonding process) and cross-cut tests (painting process). Not all tested methods were effective in increasing adhesion, especially in the adhesive bonding process, and even fewer in the painting process. However, some of them were suitable for both applications. The use of primers was found to be crucial.

Cold plasma processing of sesame milk: Changes on physicochemical properties, nutrition, anti-nutritional factors, protein structure and allergenicity

In the recent decade, consumers have preferred plant-based (vegan) foods due to the maintenance of environmental sustainability. However, some of the plant-based foods have a demerit of the presence of anti-nutritional factors and allergenic components. Thus, the current study was aimed at reducing these demerits in sesame milk without spoiling the quality by the use of green, novel, cold plasma technology. This study investigated the effect of a low-pressure plasma (LPP) system's power levels (25, 60 and 120 W) on the physicochemical properties, nutritional changes, anti-nutritional factors, protein structure and allergenicity of sesame milk. No prominent or undesirable changes were observed in the physicochemical properties; conductivity increased with the increase in power level (59.23 mS/cm in control to 61.67 mS/cm at 120 W). The lipoxygenase activity was reduced to 67 % for samples treated at 120 W LPP power. The anti-nutritional factors phytates (25 % reduction from 1.47 mg/g in control to 1.09 mg/g in 120 W) and oxalates (10 % reduction from 39.14 µg/g in control to 35.18 µg/g 120 W) decreased slightly during plasma application. The DSC and FTIR analysis revealed that plasma-induced oxidation changed the secondary protein. However, there was no significant reduction (5 %) in allergenicity during LPP treatment. Though, the plasma application was effective in reducing the enzyme activity and antinutritional factors, no drastic reduction or complete elimination was observed. An increase in power level or exposure time in future could aid in the reduction of allergenicity in sesame milk.

Plasma defect-engineering of bulk oxygen-deficient zirconia

Oxygen-deficient zirconia (ZrO2-x) has recently emerged as a promising material for light absorption and photocatalytic applications. However, the economic and environmentally friendly manufacture of bulk ZrO2-x remains challenging and has limited widespread adoption. In this study, we present a novel low-pressure (300 Pa) plasma treatment (H2 gas at 500 °C for 5 h) capable of producing fully-dense bulk ZrO2-x without significant structural modifications. EPR (electron paramagnetic resonance) and XPS (X-ray photoelectron spectroscopy) characterisation of the plasma treated zirconia indicate the formation of Zr3+ ions and F2+ (VO··) centres. The increase of oxygen vacancies is also supported by the greater exothermic heat flow and relative mass gain observed through TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry) analyses. Diffuse reflectance spectroscopy (DRS) reveals a substantial enhancement in light absorption, with an average increase of 66.2 % and >65 % absolute absorption across the entire spectrum (200–3000 nm). XPS and DRS measurements suggest significant reduction in both direct (from 4.84 to 2.61 eV) and indirect (from 3.19 to 1.45 eV) bandgap transition. By effectively enhancing the light absorption capability, reducing bandgap transitions, and maintaining the structural integrity of zirconia, low-pressure plasma treatments offer a promising and scalable approach for the environmentally friendly production of next-generation ZrO2-x materials.

Low-Pressure Plasma Treatment Increased the Quality and Characteristic Flavor of Lyophilized Lemon Slices

Low-pressure plasma (LPP) treatment was implemented as a nonthermal technology to preserve the organoleptic and nutritional qualities of lyophilized lemon slices. Effects of LPP treatment on the basic quality and flavor characteristics of lyophilized lemon slices stored for 7 d were evaluated. Fresh lyophilized lemon slices were prepared as a reference. The total titratable acids and sugars were in the range of 1.00∼1.11 mg/mL and 190.21∼197.37 mg/mL. The total phenolic content and Vc gradually decreased during storage from 1.74 to 1.33 mg/mL and 0.53 to 0.31 mg/mL. LPP had minor effects on total sugars and total titrate acids but prevented the storage losses of vitamin C (Vc) and phenols. A total of 35 volatile organic compounds were identified with C10 monoterpenoids being the major compounds. C6-C9 aldehydes corresponding to a green grassy aroma gradually decreased with increasing storage time. The gallery plot confirmed the different compositions of volatile organic compounds in LPP-treated samples. LPP-treated lemon slices had a higher content of preferred aromatic substances (terpinen-4-ol, α-terpineol, α-terpinene, and limonene) with a citrus-like flavor. These results demonstrated the positive effect of LPP treatment on retaining the flavor characteristics of lemon slices.

Effects of Different Cooking Methods on Glycemic Index, Physicochemical Indexes, and Digestive Characteristics of Two Kinds of Rice

Diets including rice and rice-cooking methods influence digestive processes and blood glucose control. In this research, the effects of three different treatments (high-temperature and low-pressure plasma cooking, high-temperature cooking at atmospheric pressure (traditional method), and high-temperature cooking at high pressure) on the texture, color, molecular structure, infrared spectrum, microstructure, debranching enzyme activity, amylopectin content, glycemic index (GI), and in vitro starch digestibility of two rice varieties were studied. The results showed that the hardness, elasticity, viscosity, and chewability of rice after the high-temperature and low-pressure plasma treatment had no obvious changes compared with the traditional cooking method. A SEM analysis showed that the physical properties of the hydrophilicity on the surface of the rice increased after the high-temperature and low-pressure plasma treatment; the debranching enzyme activity reached 3.88 U/g (Xiantao rice) and 3.81 U/g (Heyuan rice), respectively, the amylose content of raw rice reached 68.77 mg/mL (Xiantao rice) and 64.92 mg/mL (Heyuan rice), which increased by 43.31 mg/mL and 39.46 mg/mL, respectively, and the GI was within the medium glycemic index of 56–69. The resistant starch in the Heyuan and Xiantao rice varieties amounted to 88.60 ± 3.10% and 89.40 ± 3.58%, respectively, after the high-temperature and low-pressure plasma processing method. The results showed positive effects and application potential for the cooking method in respect of diabetic consumers.

Structure Modification and Enhancement of Wear Resistance of Ultra-High-Molecular-Weight Polyethylene by Low-Pressure Helium Plasma Treatment

Structure Modification and Enhancement of Wear Resistance of Ultra-High-Molecular-Weight Polyethylene by Low-Pressure Helium Plasma Treatment

Structure Modification and Enhancement of Wear Resistance of Ultra-High-Molecular-Weight Polyethylene by Low-Pressure Helium Plasma Treatment

The surface treatment of ultra-high-molecular-weight polyethylene (UHMWPE) in heliumplasma at a pressure of 0.133 mbar has been studied by IR spectroscopy, X-ray photoelectron spectroscopy,a nd atomic force microscopy. It has been shown that the helium plasma treatment leads to the formation of double bonds in the UHMWPE surface layer and the associated formation of intermolecular crosslinks. The crosslinking of the surface layer is accompanied by a decrease in the nanowear of the UHMWPE surface bymore than three orders of magnitude, which is confirmed by measurements using an atomic force microscope in the contact mode

Immediate-sustained lactate release using alginate hydrogel assembled to proteinase K/polymer electrospun fibers

This work proposes a microfibers-hydrogel assembled composite as delivery vehicle able to combine into a single system both burst and prolonged release of lactate. The prolonged release of lactate has been achieved by electrospinning a mixture of polylactic acid and proteinase K (26.0 mg of proteinase K and 0.99 g of PLA dissolved in 6 mL of 2:1 chloroform:acetone in the optimal case), which is a protease that catalyzes the degradation of polylactic acid into lactate. The degradation of microfibers into lactate reflects that proteinase K preserves its enzymatic activity even after the electrospinning process because of the mild operational conditions used. Besides, burst release is obtained from the lactate-loaded alginate hydrogel. The successful assembly between the lactate-loaded hydrogel and the polylactic acid/proteinase K fibers has been favored by applying a low-pressure (0.3 mbar at 300 W) oxygen plasma treatment, which transforms hydrophobic fibers into hydrophilic while the enzymatic activity is still maintained. The composite displays both fast (< 24 h) and sustained (> 10 days) lactate release, and allows the modulation of the release by adjusting either the amount of loaded lactate or the amount of active enzyme.