Low Pressure Oxygen Plasma Treatment Research Articles

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.

Structural Analysis of Kevlar Fabric Treated with Oxygen Plasma

The purpose of this work was to study the effects of low-pressure oxygen plasma treatment on the surface characteristics of kevlar fabric. For comparison purposes, samples treated with oxygenated plasma were prepared and characterised under different experimental conditions, i.e. a treatment time variation of 10, 30 and 60 minutes under a constant pressure of 4 mBar, using a pulsed current source. We analysed the effects of chemical and physical changes to the surface of the material aiming at improved hydrophilicity attributed to the formation of roughness on the surface of fibres, thus obtaining optimal parameters for future works. Changes in the chemical composition of the surface as well as in the superficial roughness of fibres before and after treatment were determined by FTIR, TGA, XRD and wettability testing. SEM was used as a complementary technique to monitor the changes triggered by the procedures using oxygen plasma.

Performance enhancement of perovskite solar cells via modification of the TiO2/perovskite interface with oxygen plasma treatment

High-temperature (~500 °C) sintering is a routine post-treatment to fabricate compact Titanium dioxide (TiO2) electron selective layer (ESL) in high-performance perovskite solar cells (PSCs). Here, we propose an effective low-temperature (<150°C) approach: pinhole-free and compact ultrathin TiO2 layers are fabricated via thermal atomic layer deposition (ALD) following a low-pressure oxygen plasma treatment. The hydrophilicity of TiO2 surfaces can be suitably tailored, which favors precursor solution being well spread and the growth of perovskite film. In addition, effective removal of oxygen vacancies serving as unproductive quenching sites in TiO2 surface is observed, which is attributed to atomic oxygen radical, the most reactive species generated in oxygen plasma. The PSC device with oxygen-plasma-treated ALD–TiO2 ESL achieves an efficiency of 14.9%, which is better than 13.3% of the device with 500 °C- sintered ALD–TiO2 ESL and comparable to 14.3% of the device with conventional 500°C-sintered Sol–gel–TiO2 ESL under our conditions.

Plasma modification of PU foam for piezoresistive sensor with high sensitivity, mechanical properties and long-term stability

Rapid development of artificial intelligence and wearable electronics facilitate the demand for high performance piezoresistive sensors. Not only high sensitivity but also good mechanical property as well as long-term usage are critical parameters to value piezoresistive sensors performance. In this work, a flexible, highly sensitive and versatile piezoresistive sensor with 3D porous structures, based on commercially available polyurethane (PU) foams coated with cellulose nanofiber @ carbon black (CNF@CB) conductive layer, was fabricated. We are particularly interested in the effect of interaction between the conductive filler and PU foam on the sensor performance. Thus, low-pressure oxygen plasma treatment was innovatively adopted to modify and activate PU scaffold to enhance the affinity between PU framework and CNF@CB conductive layer. Strong interfacial interaction is not only contributed to the sensitivity but also to the mechanical reinforcement of conductive foams, which is helpful to the long-term usage. The as-prepared PU/CNF@CB conductive foams exhibit very high compressive sensitivity of 0.35 kPa−1 (about 100% increase compared with the untreated ones), along with good mechanical property (29 kPa at 50% compressive strain, about 27% increase compared with the untreated ones) and electrical property (0.047 S/m). In addition, good stability and durability are demonstrated for the prepared PU/CNF@CB conductive foams especially under micro-pressure or micro-strain which is a huge challenge for bulk piezoresistive sensors. Such a kind of sensitive material combined with low-cost, flexibility, high sensitivity, duration, is very attractive in high-tech area.

Comparison of low-pressure oxygen plasma and chemical treatments for surface modifications of Ti6Al4V

Different treatments were conducted over Ti6Al4V samples in order to produce a surface modification to increase cell attachment and proliferation. The surface treatments evaluated in this study were as follows: etching with sulfuric acid/hydrochloric acid, oxidizing with hydrogen peroxide and low-pressure oxygen plasma treatment. In contrast to other works found in the literature, this research conducts a comparison between different chemical and physical treatments in terms of different assays for surface characterization: X-ray diffraction, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy, water contact angle, release of vanadium ions and cell viability tests (MTT) of human osteoblasts (hFOB 1.19). Cell morphology over the different substrates was also studied by SEM observation. It was found that plasma and peroxide treatments increase the O/Ti ratio at the titanium surface and provide an increase in cell affinity. On the other hand, acid etching provides a superhydrophilic surface which is not able to improve the cell attachment of human osteoblasts.

Performance enhancement of ultrafiltration in apple juice clarification via low-pressure oxygen plasma: A comparative evaluation versus pre-flocculation treatment

The aim of this study was to improve ultrafiltration (UF) performance during clarification of raw apple juice through surface modification of commercial polysulfone membranes (US100) by low-pressure oxygen plasma treatment (LP-OPlsT). A Plasma power of 90 W and exposure time of 10 min were determined as the most effective parameters enabling an increase in the ΔGiwi value of the plain membrane from (−) 25 ± 2 mN m−1 to (+) 30 ± 1 mN m−1. Improved hydrophilicity achieved by LP-OPlsT remarkably enhanced the performance of US100 throughout the clarification of raw apple juice without the need of an additional pre-flocculation step. While Rfrev (86%) was the dominant resistance controlling the fouling during UF of raw apple juice through the plain membrane, the contribution of Rfrev to Rt decreased to 56% after pre-flocculation step. LP-OPlsT further decreased this ratio, up to 46%, confirming the charge repulsion between the modified membrane and the foulant particles.

Optimizing the combination of MoO3 interface layer and low pressure plasma treatment on indium tin oxide (ITO) anode

In this work, we performed the investigation on surface modification of indium tin oxide (ITO) anode by depositing MoO3 interface layer and treating with low pressure plasma. Experimental results revealed both low pressure oxygen plasma treatment and MoO3 interface layer are efficient in facilitating the injection of holes, while both modifications increase the ITO surface roughness. Interestingly, the electroluminescent (EL) device with 3nm MoO3 layer displayed the highest EL performances, which were even higher than those of the device with both modifications. By optimizing the selection of gas, treatment time, and applied electric field intensity of low pressure plasma treatment, the combination of 3nm MoO3 layer and 2min low pressure nitrogen plasma treatment at 4000Vm−1 was demonstrated to be most efficient in depressing the unexpected leakage current without sacrificing the injection rate of holes.

Adhesion and Cellular Compatibility of Silicone‐Based Skin Adhesives

Pressure‐sensitive adhesives based on silicone materials have emerging potential as adhesives in healthcare products, in particular for gentle skin adhesives. To this end, adhesion to rough skin and biocompatibility are crucial factors for a successful implementation. In this study, the mechanical, adhesive, and biological properties of the two‐component poly(dimethylsiloxane) Soft Skin Adhesive MG 7‐9800 (SSA, Dow Corning) have been investigated and compared to Sylgard 184. Different mixing ratios of SSA's components allow for tuning of the shear modulus, thereby modifying the adhesive properties of the polymer. To give a comprehensive insight, the authors have analyzed the interplay between pull‐off stress, adhesion energy, and stretch of the adhesive films on smooth and rough surfaces. The focus is placed on the effects of substrate roughness and on low pressure oxygen plasma treatment of the adhesive films. SSA shows superior biocompatibility in in vitro cell culture experiments. High pull‐off stresses in the range of 3 N cm−2 on a rough surface are achieved, promising broad application spectra for SSA‐based healthcare products. image

PCL/PHBV blended three dimensional scaffolds fabricated by fused deposition modeling and responses of chondrocytes to the scaffolds.

In this study, poly(ε-caprolactone)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PCL/PHBV) blended porous scaffolds were fabricated by fused deposition modeling (FDM). PCL/PHBV filaments, initially prepared at different weight ratios, that is, 100/0, 75/25, 50/50, and 25/75, were fabricated by the lay-down pattern of 0/90/45/135° to obtain scaffolds with dimension of 6.0 × 6.0 × 2.5 mm3 and average filament diameters and channel sizes in the ranges of 370-390 µm and 190-210 µm, respectively. To enhance the surface hydrophilicity of the materials, the scaffolds were subsequently subjected to a low pressure oxygen plasma treatment. The untreated and plasma-treated scaffolds were comparatively characterized, in terms of surface properties, mechanical strength, and biological properties. From SEM, AFM, water contact angle, and XPS results, the surface roughness, wettability, and hydrophilicity of the blended scaffolds were found to be enhanced after plasma treatment, while the compressive strength of the scaffolds was scarcely changed. It was, however, found to increase with an increasing content of PHBV incorporated. The porcine chondrocytes exhibited higher proliferative capacity and chondrogenic potential when being cultured on the scaffolds with greater PHBV contents, especially when they were plasma-treated. The PCL/PHBV scaffolds were proven to possess good physical, mechanical, and biological properties that could be appropriately used in articular cartilage regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1141-1150, 2017.

Invited: Atmospheric Pressure Plasma Modified Polyaniline Crystals for Detection of Volatile Organic Compounds

Among the family of conducting polymers, polyaniline (PANI) is the most studied due to an easy and low-cost synthesis, good environmental stability, and simple doping/dedoping process based on acid/base reactions.1,2 PANI polymer can be used for different applications including in solar cells, artificial muscles, gas sensors, capacitors, acid-base indicators, etc.3 The nature of PANI conductivity is explained by its ability to form polarons and cation radicals.3,4 Moreover PANI shows significant variations in conductivity when exposed to various volatile organic compounds (VOC).4 This property arises from to the doping-dedoping of conducting PANI layer, which makes it suitable for detection of wide variety of gas molecules.Changes in the chemical states can alter the sensitivity and selectivity of PANI layer. Chemical modifications by doping of PANI with various acid dopants, co-polymerisation with various thermoplastics, co-polymerisation with aniline derivatives or enzymatic polymerisation of aniline has been used to improve the processability and solubility of PANI as reviewed by Jaymand et.al.5. Another techique is low pressure plasma treatment which has been reported to be an efficient technique for the carbon functionalization as well as changing the chemical states of the PANI surface.6,7 The variations of the chemical changes induced by low pressure oxygen plasma treatment efficiently enhanced the selectivity and sensitivity towards various gases.8 PANI exposed to various plasmas has demonstrated also increased resistivity.Urea is widely used in the manufacture of explosives and nitrogen fertilisers in industries. Eventhough expoure of urea vapor is harmless at lower concentrations, prolonged exposure of urea can cause irritations to eyes, skin or respiratory systems. We demonstrated a reusable sensor based on emeraldine polyaniline crystals coated on polyethylene terephthalate substrate at room temperatue. To enhance the signal response, we used an atmospheric pressure He plasma treatment which showed pronounced and steady increase in the signal response for six consecutive cycles. The surface changes as well as mechanism of detection after plasma treatement were studied by various analysis techniques including FT-IR, scanning electron microscopy (SEM), and X-ray photoelectron microscopy (XPS).Macdiarmid A.G., Chiang J.C., Richter A.F., Epstein A.J., Synthetic Metals., 18 (1987), 285;Hao B., Li L., Wang Y., Qian H., Tong G., Chen H., Chen K., Journal of Applied Polymer Science 127 (2013), 4273;Sambhu B., Dipak K., Nikhil K.S., Joong H.L., Progress in Polymer Science 34 (2009), 783;Ayad M.M., El-Hefnawey G., Torad N.L., Journal of Hazardous Materials 168 (2009), 85;Jaymand M., Progress in Polymer Science 38 (2013), 1287;Kang E.T., Ma Z.H., Tan K.L., Zhu B.R., Uyama Y., Ikada Y., Polymers for Advanced Technologies 10 (1999), 421;Kang E.T., Kato K., Uyama Y., Ikada Y., Journal of Materials Research 11 (1996), 1570;Kunzo P, Lobotka P, Micusik M and Kovacova E Sensors and Actuators B: Chemical 171–172 (2012), 838;

Characterisation of surface properties of chemical and plasma treated regenerated cellulose fabric

The aim of this research work was to study the surface properties and sorption characteristics of differently treated regenerated cellulose fabrics. Surface modifications of viscose, modal and lyocell samples caused by using standard chemical pre-treatment procedures were compared to an alternative activation procedure by applying low pressure oxygen plasma treatment. The elemental chemical composition of the modified fabric surfaces was investigated using X-ray photoelectron spectroscopy (XPS), while hydrophilic/hydrophobic properties were evaluated by determining the water contact angles, as well as thoroughly analysed using Owens–Wendt surface energy (SFE) and surface polarity investigations. Standard chemical and also plasma treatments changed the surface chemistry of cellulose. Bleaching and alkaline treatments increased the surface carboxylic acid content by approximately 4.8% while plasma treatment increased it by approximately 9.7%. As a consequence, higher hydrophilicity arises as proved by water contact angle decrease; i.e. 24% (61°) after standard chemical treatments and 70% (20°) after plasma treatment. Both chemical treatments increase the SFE and polar components, while the reduction of dispersive components was less pronounced. The oxygen activation treatment has the greatest influence on the SFEs of the samples as well as on polarity of the samples.

Oxygen plasma treatment and deposition of CNx on a fluorinated polymer matrix composite for improved erosion resistance

The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CNx coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CNx was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relative to the surface. In situ x-ray photoelectron spectroscopy was used to evaluate the effect of the plasma treatment on surface chemistry, and electron microscopy was used to identify changes in the surface morphology of the PMC substrate after plasma exposure. The fluorine concentration at the surface was significantly reduced and the carbon fibers were exposed after plasma treatment. CNx coatings were then deposited on oxygen treated PMC substrates. Qualitative tests demonstrated that plasma treatment improved coating adhesion resulting in an erosion resistance improvement of a factor of 2 compared to untreated coated composite substrates. The combination of PMC pretreatment and coating with CNx reduced the erosion rate by an order of magnitude for normally incident particles.

Polymer Surface Treatment by Atmospheric Pressure Low Temperature Surface Discharge Plasma: Its Characteristics and Comparison with Low Pressure Oxygen Plasma Treatment

The polymer treatment with a low-temperature plasma jet generated onthe atmospheric pressure surface discharge (SD) plasma is performed.The change of the surface property over time, in comparison with lowpressure oxygen (O2) plasma treatment, is examined. As onecompares the treatment by atmospheric pressure plasma to that by thelow pressure O2 plasma of PS (polystyrene) the treatment effectswere almost in complete agreement. However, when the atmosphericpressure plasma was used for PP(polypropylene), it producedremarkablehydrophilic effects.

Plasma-bonding of poly(dimethylsiloxane) to glass

AbstractFor the purpose of bonding poly(dimethylsiloxane) (PDMS) to glass, both components’ surfaces were treated with low-pressure oxygen plasma, indirect corona or simply with an oxygen-rich butane gas flame. In the case of low-pressure oxygen plasma treatment, the process parameters were varied and optimized with the consequence that the achieved adhesion between PDMS and the glass substrate was so strong that the PDMS could not be peeled off the glass slide without damaging the elastomer.