Atmospheric Plasma Pretreatment Research Articles

Impact of Cold Atmospheric Plasma Pretreatment on the Recovery of Phenolic Antioxidants from Spent Coffee Grounds

AbstractIn the present study, cold atmospheric plasma (CAP) was employed as a pretreatment method for the extraction of phenolic compounds from spent coffee grounds (SCGs). The impact of CAP treatment conditions, i.e., thickness of the SCGs layer (mm), distance between the plasma source and the SCGs layer (mm) and duration of CAP treatment (min), on the total phenol content, in vitro antioxidant activity, as well as caffeine and chlorogenic acid content of SCGs, was investigated. The process parameters were optimized with the aid of response surface methodology (RSM). After optimizing the CAP pretreatment conditions, the CAP-treated SCGs were subjected to ultrasound-assisted extraction using ethanol as the extraction solvent. The optimum conditions for CAP treatment identified, i.e., thickness, 1 mm; distance, 16 mm; and duration, 15 min, led to a significant enhancement in the recovery of bioactive compounds from SCGs compared to those obtained from untreated SCGs. Total phenolic content and antioxidant activity significantly increased (i.e., TPC from 19.0 ± 0.7 to 24.9 ± 1.4 mg GAE/100 g dry SCGs, ADPPH from 106.7 ± 5.01 to 112.3 ± 4.3 μmol Trolox/100 g dry SCGs, AABTS from 106.7 ± 5.01 to 197.6 ± 5.8 μmol Trolox/100 g dry SCGs, ACUPRAC from 17938 ± 157 to 18299 ± 615 μmol Trolox/100 g dry SCGs). A significant increase in caffeine content from 799.1 ± 65.1 mg to 1064 ± 25 mg/100 g dry SCGs and chlorogenic acid content from 79.7 ± 15.3 mg to 111.3 ± 3.3 mg/100 g dry SCGs, was also observed. Overall, CAP pre-treatment can be used to enhance the recovery of bioactive compounds from SCGs.

The effect of cold atmospheric plasma pretreatment on oil absorption, acrylamide content and sensory characteristics of deep-fried potato strips

This study investigated the impact of 60 kV Cold Atmospheric Plasma (CAP) pretreatment for varying durations (5, 10, and 15 min) on potato strip characteristics before and after frying, emphasizing oil uptake, acrylamide formation. Potato samples treated with cap showed significantly better physicochemical characteristics. Scanning electron microscopy revealed deformation of cell wall due to CAP treatment. Fourier-transform infrared spectroscopy indicated structural changes, while X-ray diffraction analysis suggested that starch remained amorphous state in CAP-pretreated samples. Post-frying, CAP-treated potato strips exhibited altered oil distribution with reduced absorption, possibly due to microstructural changes. CAP substantially reduced acrylamide formation during frying by degrading asparagine and inactivating amylase. CAP affected strip color, with increased brightness and decreased redness and yellowness after 14 days. Sensory evaluation showed no significant difference, with prolonged CAP-treated strips receiving higher overall acceptability scores. These findings highlight CAP as a non-thermal technology to enhance fried potato product quality and safety.

Effects of cold atmospheric plasma pre-treatment on maintaining the quality of ready-to-eat drunken red shrimp (Solenocera crassicornis) stored at chilled conditions

This present study investigated the effect of cold atmospheric plasma (CAP) pre-treatment on the quality of ready-to-eat drunken red shrimp (Solenocera crassicornis) during chilled storage. The shrimp were pre-treated with the CAP at 40 kV and 36 kH for 100 s in a plasma generating equipment before the drunken treatment and compared with an untreated control sample. The results showed that the CAP pre-treatment significantly inhibited the total viable count (TVC) values, total volatile basic nitrogen (TVB-N) content, and polyphenol oxidase (PPO) activity of the drunken shrimp compared to the control treatment. Furthermore, the CAP pre-treatment also significantly maintained the myofibrillar protein (MP) content, texture properties, and a more stable histological structure of muscle fibers compared to the control. High-throughput sequencing results confirmed that the CAP pre-treatment significantly reduced the diversity and abundance of several bacteria in the shrimp. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis detected that the CAP pre-treatment effectively maintained the stability of volatile organic compounds (VOCs). These findings provide valuable theoretical support for the processing and storage of drunken shrimp.

Cold Plasma Technology for Tomato Processing By-Product Valorization: The Case of Tomato Peeling and Peel Drying

The tomato processing industry is focused on product yield maximization, keeping energy costs and waste effluents to a minimum while maintaining high product quality. In our study, cold atmospheric plasma (CAP) pretreatment enhanced tomato processing to facilitate peelability, a specific peeling process, and enhance peel drying. Peeling force analysis determined that CAP pretreatment of whole tomatoes improved peelability under the conditions used. The specific peeling force after CAP treatment decreased by more than three times. It was observed that cold atmospheric plasma pretreatment reduced the duration of infrared drying of tomato peels by 18.2%. Along with that, a positive effect on the reduction of the specific energy consumption of peel drying was shown for CAP-pretreated tomato peels. The obtained data show that the technology of cold atmospheric plasma pretreatment, in particular, when processing whole tomatoes and tomato peels, has a promising application in industry, as it can significantly reduce the specific energy consumption for peeling and drying procedures.

Effects of Cold Atmospheric Plasma Pre-Treatment of Titanium on the Biological Activity of Primary Human Gingival Fibroblasts

Cold atmospheric plasma treatment (CAP) enables the contactless modification of titanium. This study aimed to investigate the attachment of primary human gingival fibroblasts on titanium. Machined and microstructured titanium discs were exposed to cold atmospheric plasma, followed by the application of primary human gingival fibroblasts onto the disc. The fibroblast cultures were analyzed by fluorescence, scanning electron microscopy and cell-biological tests. The treated titanium displayed a more homogeneous and denser fibroblast coverage, while its biological behavior was not altered. This study demonstrated for the first time the beneficial effect of CAP treatment on the initial attachment of primary human gingival fibroblasts on titanium. The results support the application of CAP in the context of pre-implantation conditioning, as well as of peri-implant disease treatment.

Plasma enhanced inkjet printing of particle-free silver ink on polyester fabric for electronic devices

Most formulations of metal inks comprise of a suspension of nanoparticles however, these suffer when printed by the formation of unwanted agglomeration. The exploration and optimisation of particle-free silver-complex ink is causing a strong demand for inkjet printing of these formulations over nanoparticle-based suspension inks. This is due to the enhanced printability and rapid conversion via thermal reduction into a conductive material, which can be utilised in electronics manufacture. We developed a silver-complex ink for ‘smart-clothing’ through inkjet printing. The high-quality printing - characterised by no satellite droplet formation and fast speed - is demonstrated upon polyester fabric by the formation of electrical circuitry using a thermal reduction process. Fabric printing is limited by good metal coverage and adhesion, which we demonstrate and improve on in the work by the application of a low temperature, atmospheric air plasma pre-treatment to the polyester surface, which improves printed silver density and coverage using a plasma device which is easy to operate and economic. Printed silver layer reduction and film crystallinity is characterised from high resolution scanning electron microscopy, and spectroscopy (Ultraviolet-visible and Raman) detailing growth mechanisms for high track feature conductivity, producing a low sheet resistivity of 1.378 ± 0.001 Ω/□ and by the lighting of a 1.9 V, 250 mA Light Emitting Device, highlighting its application for conductive features processing. • Conductive films on PET fabric. • Ink jet printing particle-free silver-complex ink. • Conductive thin Ag films, 1.378 ± 0.001 Ω/□. • Enhancement of printed density and coverage by atmospheric plasma pre-treatment.

Influences of cold atmospheric plasma pretreatment on drying kinetics, structural, fractional and chemical characteristics of tobacco leaves

Cold atmospheric plasma (CAP) treatment is a promising technology for the processing of agricultural products. The effect of cold atmospheric plasma pretreatment on the drying rate and quality of tobacco leaves (Virginia 202) during natural drying were studied. Naturally dried tobacco leaves were analyzed for their microstructural changes, fractional composition, and chemical composition. It was observed that cold atmospheric plasma pretreatment reduces the duration of natural drying of tobacco leaves by 37.7% and 19.5% for a leaf vein and for entire lamina of a leaf respectively. Along with that, a positive effect on increase in fiber yield during fractional analysis was shown for CAP pretreated tobacco leaves. Chemical analysis determined that CAP pretreatment of tobacco leaf improved the carbohydrate:protein ratio, increased the Schmuck’s value from 0.8 to 1.3 when processing tobacco leaf veins, but reduced the Schmuck’s value to 0.3 when processing the entire lamina of tobacco leaf. It is shown that nicotine content of dried tobacco leaves can be decreased by CAP treatment and controlled by applying to whole leaf or leaf vein only. The obtained data show that technology of cold atmospheric plasma pretreatment, in particular, when processing the vein (midrib) of a tobacco leaf has a promising application in industry, as it can significantly reduce the drying time of the leaves and affect the qualitative composition of the final product obtained in result.

Analgesic effect of topical lidocaine is enhanced by cold atmospheric plasma pretreatment in facial CO2 laser treatments.

Topical anesthesia is widely used in many dermatological and cosmetic procedures. Nevertheless, the stratum corneum serves as the skin barrier, impedes the transdermal drug delivery greatly, and results in insufficient analgesia. Cold atmospheric plasma (CAP) has been researched as a transdermal drug delivery promoter with ex vivo experiments for a few years, while clinical trials are scarce. To assess the efficacy and safety of CAP as a pretreatment to improve the transdermal absorption of topical anesthetic cream before the CO2 laser treatment for postacne scars in the human body. Twenty patients, seeking full facial laser treatment for atrophic acne scars, underwent a randomized split-face study. One side of the face was pretreated by CAP before topical anesthetic cream was applied, and the other side was applied with topical anesthetic cream only as control. After that, the subjects went through full-face fractional CO2 laser treatment of postacne scars. They were asked to score the pain on a visual analogue scale (VAS) after the laser treatment to measure the anesthesia effects which indicates the transdermal absorption of the cream. Possible adverse effects of the plasma were recorded during the pretreatment including associated pain, heat, erythema, and edema. The VAS score of the treated side was statistically lower (5.1±2.1) compared with the nontreated side (6.3±1.9), with a mean difference of 1.3 (95% confidence interval [CI], 0.6-1.9; P<.0001). No severe adverse event was reported, and all the disturbing sensations and symptoms (pain, heat, and edema) were evaluated as mild with no mean score surpassing 4.0. Plasma pretreatment of 5minutes before topical anesthetic cream application gives significant pain reduction during the laser procedures, showing the potential effects of CAP on promoting transdermal drug delivery, with no obvious adverse effects reported.

Adhesive bonding of 3D-printed plastic components

ABSTRACTTensile strength of adhesive bonds with three different commercial epoxy resins and laser sintered polyamide 12 (PA 12) has been evaluated by means of Centrifugal Adhesion Testing Technology (CATT, LUMiFrac Adhesion Analyzer). Different post treatment states (as received and chemically smoothed) and pre-treatment states (as received and atmospheric plasma) of the PA 12 surface have been considered. It has been shown that the epoxy resins infiltrate the surface porosity of the laser sintered material, which leads to a special fracture pattern. Tensile strength of the adhesive bonds has been significantly improved after atmospheric plasma pretreatment. Chemical smoothing had a neglicable effect on the tensile strength of the tested specimens, but lead to a change in fracture pattern, especially without atmosphric plasma pretreatment.

Prevention of bacterial colonization on non-thermal atmospheric plasma treated surgical sutures for control and prevention of surgical site infections.

Surgical site infections have a remarkable impact on morbidity, extended hospitalization and mortality. Sutures strongly contribute to development of surgical site infections as they are considered foreign material in the human body. Sutures serve as excellent surfaces for microbial adherence and subsequent colonization, biofilm formation and infection on the site of a surgery. Various antimicrobial sutures have been developed to prevent suture-mediated surgical site infection. However, depending on the site of surgery, antimicrobial sutures may remain ineffective, and antimicrobial agents on them might have drawbacks. Plasma, defined as the fourth state of matter, composed of ionized gas, reactive oxygen and nitrogen species, free radical and neutrals, draws attention for the control and prevention of hospital-acquired infections due to its excellent antimicrobial activities. In the present study, the efficacy of non-thermal atmospheric plasma treatment for prevention of surgical site infections was investigated. First, contaminated poly (glycolic-co-lactic acid), polyglycolic acid, polydioxanone and poly (glycolic acid-co-caprolactone) sutures were treated with non-thermal atmospheric plasma to eradicate contaminating bacteria like Staphylococcus aureus and Escherichia coli. Moreover, sutures were pre-treated with non-thermal atmospheric plasma and then exposed to S. aureus and E. coli. Our results revealed that non-thermal atmospheric plasma treatment effectively eradicates contaminating bacteria on sutures, and non-thermal atmospheric plasma pre-treatment effectively prevents bacterial colonization on sutures without altering their mechanical properties. Chemical characterization of sutures was performed with FT-IR and XPS and results showed that non-thermal atmospheric plasma treatment substantially increased the hydrophilicity of sutures which might be the primary mechanism for the prevention of bacterial colonization. In conclusion, plasma-treated sutures could be considered as novel alternative materials for the control and prevention of surgical site infections.

Application of cold plasma to develop carboxymethyl cellulose-coated polypropylene films containing essential oil

This study was aimed to develop and characterize carboxymethyl cellulose-coated polypropylene (PP/CMC) films with Zataria multiflora essential oil (ZEO) as a new antimicrobial food packaging. For better attachment of CMC on polypropylene (PP) film surface, atmospheric plasma pretreatment was used. Results showed the formation of polar groups such as CO and OH in the PP surface following the plasma treatment. Plasma-treated PP had rougher surfaces and their contact angle reduced from 88.92° to 52.15° indicating increased surface hydrophilicity. Plasma-treated PP/CMC films showed lower water vapor permeability (WVP) and higher tensile strength compared to untreated bilayer films. Results revealed that antimicrobial PP/CMC films with higher content of ZEO had lower WVP, but was more sensitive to breakage. Antimicrobial characteristics in the direct contact and vapor phase represented great inhibition for all the tested bacteria. Our findings suggest that plasma-treated PP/CMC films have the potential for application in food antimicrobial packaging.

Improved Adhesion of Dense Silica Coatings on Polymers by Atmospheric Plasma Pretreatment

Oxygen atmospheric plasma was used to pretreat polycarbonate (PC) and stretched poly(methyl methacrylate) (PMMA) surfaces in order to enhance the adhesion of the dense silica coatings deposited by atmospheric plasma on the polymer substrates. The treatment time and chemical structure of the polymers were found to be important factors. For PC, a short treatment increased the adhesion energy, while longer treatment times decreased the adhesion. In contrast, plasma pretreatment monotonically decreased the adhesion of PMMA, and pristine PMMA exhibited much higher adhesion than the PC counterpart. We found that adhesion enhancement was achieved through improved chemical bonding, chain interdiffusion, and mechanical interlocking at the coating/substrate interface, after a short atmospheric plasma treatment. Decreased adhesion resulted from overoxidation and low-molecular-weight weak layer formation on the polymer surface by prolonged atmospheric plasma treatment. The dramatic differences in the behavior of PC and PMMA in relation to the plasma treatment time were due to their dissimilar resistance to atmospheric plasma exposure.

Atmospheric plasma application to improve adhesion of electrospun nanofibers onto protective fabric

Nylon 6 electrospun nanofibers were deposited on plasma-pretreated woven fabric substrates with the objective of improving adhesion between them. The prepared samples were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength, flex resistance, and abrasion resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates due to atmospheric plasma pretreatment. The samples also exhibited good flex and abrasion resistance characteristics. X-ray photoelectron spectroscopy and water contact angle analyses indicate that plasma pretreatment introduces radicals, increases the oxygen content on the substrate surface, and leads to formation of active chemical sites that may be responsible for enhanced cross-linking between the substrate fabric and the electrospun nanofibers, which in turn increases the adhesion properties. The work demonstrates that the plasma treatment of the substrate fabric prior to deposition of electrospun nanofiber mats is a promising method to prepare durable functional materials.

Novel atmospheric plasma enhanced chitosan nanofiber/gauze composite wound dressings

AbstractElectrospun chitosan nanofibers were deposited onto atmospheric plasma treated cotton gauze to create a novel composite bandage with higher adhesion, better handling properties, enhanced bioactivity, and moisture management. Plasma treatment of the gauze substrate was performed to improve the durability of the nanofiber/gauze interface. The chitosan nanofibers were electrospun at 3–7% concentration in trifluoroacetic acid. The composite bandages were analyzed using peel, gelbo flex, antimicrobial assay, moisture vapor transmission rate, X‐ray photoelectron spectroscopy (XPS), absorbency, and air permeability tests. The peel test showed that plasma treatment of the substrate increased the adhesion between nanofiber layers and gauze substrate by up to four times. Atmospheric plasma pretreatment of the gauze fabric prior to electrospinning significantly reduced degradation of the nanofiber layer due to repetitive flexing. The chitosan nanofiber layer contributes significantly to the antimicrobial properties of the bandage. Air permeability and moisture vapor transport were reduced due to the presence of a nanofiber layer upon the substrate. XPS of the plasma treated cotton substrate showed formation of active sites on the surface, decrease in carbon content, and increase in oxygen content as compared to the untreated gauze. Deposition of chitosan nanofibers also increased the absorbency of gauze substrate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Multifunctional and durable nanofiber‐fabric‐layered composite for protective application

AbstractA multifunctional and durable nanofiber‐fabric‐layered composite (NFLC) material was prepared by depositing electrospun Ag/PAN hybrid nanofibers onto a Nylon/cotton 50: 50 fabric substrate. The NFLCs showed excellent aerosol barrier efficiency and good air/moisture permeability. In addition, they showed excellent antibacterial efficiency by completely inhibiting the growth of both Gram‐negative E. coli and Gram‐positive S. aureus. The interfacial adhesion between the nanofiber layer and fabric substrate was significantly improved by atmospheric plasma pretreatment of the substrate. The resultant NFLCs showed excellent resistance to peeling, twisting, and flexing forces. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

OPTIMIZACIÓN DEL TRATAMIENTO POR PLASMA ATMOSFÉRICO SOBRE LÁMINAS DE POLIETILENO DE BAJA DENSIDAD

The vast majority of polymers and composites have low surface energy; this is due to the low presence of functional groups on their surface which results in low adhesive properties. In order to modify this intrinsic property chemical and physical processes are commonly used. These processes resent disadvantages, such as the use of products harmful to the environment. An alternative to these processes is the use of plasma technology. The main objective of this study is the improvement of the adhesive properties of the low density polyethylene (LDPE). In order to achieve the target, atmospheric plasma pretreatment has been optimized in order to promote subsequent adhesion processes, as the ones needed in the toy industry or the application of dyes or printing on surfaces.Plasma surface treatment is a clean process from the environmental viewpoint. This process does not emit any residue and it is easy to implement in an industrial process. Moreover the atmospheric plasma treatment is suitable to be applied in a large variety of materials even at high speeds when the treatment lasts less than a few seconds.In the present study it is examined the physical and chemical processes that occur in the LDPE surface as function of speed rate and distance of treatment. An increase both of the polar groups on the surface and the roughness after the treatment may increase its adhesive properties. It has been analyzed the influence of the speed rate and the nozzle distance on the final results. The adhesive properties have been evaluated using the T-peel test. The results show that at low speeds rates and low nozzle/substrate distance there is a greater inclusion of polar molecules at the surface. Consequently the adhesion properties of LDPE are improved.

Investigation and demonstration of the durability of air plasma pre-treatment on polypropylene automotive bumpers

Higher utilisation of low-density materials such as polymers and polymer composites is a pre-requisite for the lightweight vehicle of the future. Of the commodity polymers polypropylene (PP) is by far the most attractive for the automotive industry. Additionally, PP can be utilised as a glass or mineral filled composite which may be used for semi-structural applications.A major problem is that PP (along with other polyolefins) has a non-polar surface chemistry which means the wetting characteristics of components made from this material are poor. Ultimately, this will result in poor adhesion of paints, coatings or adhesive bonding products. This problem has been overcome in the majority of instances by treating the surface of the substrate in order to alter the surface chemistry.PP has found extensive use as films and flat sheets and hence certain techniques such as flame and corona have been favoured despite both having problems of heterogeneous or patchy treatment across a surface. However, for complex 3-D automotive shapes, such as bumpers, these methods are less useful. While flame treatment for example is widely used it has several disadvantages in a commercial volume production environment which all centre around the potential for the part to undergo overtreatment, incipient melting or melting during machine stops etc., as well as the hazards associated with combustible gas. An alternative method is atmospheric plasma pre-treatment.This work has investigated the effect of a forced air plasma pre-treatment on surface chemistry and bond strength of a commercial grade polypropylene material.The plasma head was attached to a robot arm which makes it highly suited to continuous production environments and can treat complex surfaces. A range of translation speeds were investigated and the surface chemistry and topography of the treated surfaces were examined using atomic force microscopy and X-ray photoelectron spectroscopy. The processing was further optimised by single lap-shear testing.An optimised set of parameters was used to pre-treat and bond a full size automotive bumper assembly with a polyurethane (PU) adhesive. Bumpers were then subjected to a standard automotive range of climate conditioning as well as soaking at −20°C and 70°C before front centre impact testing. Parts pre-treated and bonded using this pre-treatment and adhesive system, successfully passed all the required standard automotive impact tests.For added benefit, it was also found that the open time of the pre-treatment was 1 week depending on storage conditions.