Plasma-treated Substrates Research Articles

Atmospheric plasma treatment effect on shear strength of GFRP-Aluminum adhesively bonded lap joints

The objective of this study is to investigate the effect of air (dielectric barrier discharge) DBD plasma treatment on the bonding strength of adhesively bonded glass fiber-reinforced epoxy composite-aluminum lap joints. The bonding performance of lap joints produced by the plasma treatment was compared with that of untreated and peel-ply surface treatments. Water contact angles of the substrates were measured for untreated, peel-ply, and plasma surface-treated substrates. Experimental results showed that plasma-treated aluminum and GFRP substrates increased the wettability properties and thus shear strength of adhesively bonded GFRP-Al joints increased. After the shear tests, the fracture surfaces of the substrates were visually examined and three different damage modes were observed, including light fiber tear failure, adhesive failure, and thin layer cohesive failure modes.

Organic Mixed Ionic-Electronic Conductors Based on Tunable and Functional Poly(3,4-ethylenedioxythiophene) Copolymers.

Organic mixed ionic-electronic conductors (OMIECs) are being explored in applications such as bioelectronics, biosensors, energy conversion and storage, and optoelectronics. OMIECs are largely composed of conjugated polymers that couple ionic and electronic transport in their structure as well as synthetic flexibility. Despite extensive research, previous studies have mainly focused on either enhancing ion conduction or enabling synthetic modification. This limited the number of OMIECs that excel in both domains. Here, a series of OMIECs based on functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) copolymers that combine efficient ion/electron transport with the versatility of post-functionalization were developed. EDOT monomers bearing sulfonic (EDOTS) and carboxylic acid (EDOTCOOH) groups were electrochemically copolymerized in different ratios on oxygen plasma-treated conductive substrates. The plasma treatment enabled the synthesis of copolymers containing high ratios of EDOTS (up to 68%), otherwise not possible with untreated substrates. This flexibility in synthesis resulted in the fabrication of copolymers with tunable properties in terms of conductivity (2-0.0019 S/cm) and ion/electron transport, for example, as revealed by their volumetric capacitances (122-11 F/cm3). The importance of the organic nature of the OMIECs that are amenable to synthetic modification was also demonstrated. EDOTCOOH was successfully post-functionalized without influencing the ionic and electronic transport of the copolymers. This opens a new way to tailor the properties of the OMIECs to specific applications, especially in the field of bioelectronics.

Robust, Sprayable, and Multifunctional Hydrogel Coating through a Polycation Reinforced (PCR) Surface Bridging Strategy.

The sprayable hydrogel coatings that can establish robust adhesion onto diverse materials and devices hold enormous potential; however, a significant challenge persists due to monomer hydration, which impedes even coverage during spraying and induces inadequate adhesion post-gelation. Herein, a polycation-reinforced (PCR) surface bridging strategy is presented to achieve tough and sprayable hydrogel coatings onto diverse materials. The polycations offer superior wettability and instant electrostatic interactions with plasma-treated substrates, facilitating an effective spraying application. This PCR-based hydrogel coatings demonstrate tough adhesion performance to inert PTFE and silicone, including remarkable shear strength (161±49kPa for PTFE), interfacial toughness (198±27Jm-2 for PTFE), and notable tolerance to cyclic tension (10000 cycles, 200% strain, silicone). Meanwhile, this method can be applied to various hydrogel formulations, offering diverse functionalities, including underwater adhesion, lubrication, and drug delivery. Furthermore, the PCR concept enables the conformal construction of durable hydrogel coatings onto sophisticated medical devices like cardiovascular stents. Given its simplicity and adaptability, this approach paves an avenue for incorporating hydrogels onto solid surfaces and potentially promotes untapped applications.

Enhancing NO degradation in visible light through plasma-treated photocatalytic substrates featuring TiO<sub>2</sub>@g-C<sub>3</sub>N<sub>4</sub> Z-scheme structure

In this study, a novel approach is introduced involving grafting and dip coating on photocatalytic substrates to create a Z-Scheme structure of TiO<sub>2</sub>@g-C<sub>3</sub>N<sub>4</sub> (TC). The synthesized photocatalyst undergoes comprehensive characterization through techniques such as XRD, SEM, XPS, FTIR, Contact Angle Goniometer, and BET analysis. Two configurations, TC coated on PVDF membrane (TC-PVDF) and TC coated on Film (TC-Film), are evaluated for the photodegradation of NO<sub>x</sub> under visible light. Compared to the benchmark material TiO<sub>2</sub>, TC-PVDF nanoparticles demonstrate outstanding performance, boasting a specific surface area of 60.93 m<sup>2</sup>/g and minimal toxic NO<sub>2</sub> byproducts, with concentration as low as 3.54 ppb, constituting only 0.46% during NO<sub>x</sub> remediation. These nanoparticles exhibit remarkable stability, with less than a 10% decrease in efficiency after 5 cycles of visible light irradiation. Plasma treatment transforms TC-PVDF from superhydrophobic to hydrophilic, with a contact angle reduction from 124.7° to 0°. Notably, TC-PVDF shows substantial efficiency enhancements, reaching 84.04%. This study broadens insights into catalytic bag filters, providing practical implications for their use in NO<sub>x</sub> removal. It offers innovative solutions for air purification, addressing environmental challenges and advancing sustainable technologies.

Enhancing wettability and adhesive properties of PVDF-based substrates through non-thermal helium plasma surface modification

Polyvinylidene fluoride (PVDF) has gained attention as a promising material for tissue engineering due to its biocompatibility and piezoelectricity. However, achieving proper cell adhesion to PVDF surfaces remains a challenge. This study focuses on the preparation and characterization of PVDF-based substrates, including PVDF thin films and nanocomposites incorporating CoFe2O4 magnetic nanoparticles. Helium plasma treatment is employed to modify the surface properties of these substrates. The plasma treatment induces significant changes in the topography of the PVDF-based nanocomposites. The roughness values of the samples increase from 2–3 nm to 14–17 nm after 90 s of plasma treatment, leading to enhanced hydrophilicity with an average contact angle below 60°. Importantly, the helium plasma treatment preserves the magnetic and structural properties of the substrates, suggesting the retention of their magnetoelectric properties and, thus treated composites hold potential for remote stem cell activation. We provide evidence of cytocompatibility and improved adhesive properties of plasma-treated substrates using human mesenchymal stem cell cultures.

Tack Properties of Nanostructured Epoxy-Amine Resins on Plasma-Treated Glass Substrates.

A probe tack test, coupled with in situ imaging, was used to evaluate the influence of an air plasma treatment on glass substrates on the fracture energy of nanostructured epoxy-amine resins. Nanostructuration was achieved by the addition of thermoplastic triblock copolymers. The influence of the surface treatment was assessed by splitting the fracture energy (tack energy) into three main contributions (cavitation, viscous flow, and stretch). We showed that before gelation, the interfacial strength depended on the nature of the copolymers and on their interaction with grafted functions (R-COOH and R-C=O) by air plasma treatment. The latter also influenced the cohesion of the resins, impacting the copolymers' phase separation and, as a consequence, conversion rate. The tack test, coupled with rheology and thermal (differential scanning calorimetry) measurements, was relevant to explain how the balance of interactions contributed to the fracture energy up to the gel point.

Effects of surface treatment method and fabric type on adhesion between PP material and artificial fabrics

Polypropylene (PP) is an exceptional engineering plastic owing to its cost-effectiveness, durability, lightweight nature, high heat resistance, and chemical stability. It is commonly bonded with fabrics to enhance its aesthetic appeal, particularly when used in automotive interiors and various other applications. Therefore, it is necessary to ensure strong adhesion between the PP substrate and fabric. In this study, we analyze the impact of various surface-treatment methods on the surface properties and adhesive strength of PP substrates, with the objective of increasing the bond strength between PP injection-molded products and artificial leather fabrics. In this study, woven and nonwoven fabric-type artificial leather fabrics, composed of polyurethane, are used. The PP substrate is subjected to three surface treatment methods: plasma, flame, and primer coating treatments. Surface analyses are performed to assess the effect of each treatment method, and adhesive strength measurements are performed using a adhesive to bond the PP substrate and fabrics. The adhesive strengths and peel morphologies are thoroughly examined. The results indicate that the plasma-treated PP substrates exhibit the highest adhesive strengths. The findings of this study can provide valuable guidance for enhancing the adhesion between PP injection-molded products and fabrics for various industrial applications.

Mechanical characterization of solder interconnections on functionalized, copper-containing polymer thick-film pastes for hybrid integration

In this work, on different substrate materials thermally cured polymer thick-film (PTF) pastes are connected to surface mount technology resistors using a SnBiAg solder alloy. The effect of substrate pre-treatment with atmospheric plasma and thermal cycling on the shear strength of these interconnections is investigated, and the shear forces obtained are graded using United States Defense Standard / Military Standard (MIL-STD) 883. In particular, the build-up of solder interconnections on conductive structures made of commercially available copper-containing PTF pastes and their mechanical characterization is novel. As well as the mechanical characterization of conductive structures, made of PTF pastes, on plasma-treated substrates and their grading using the MIL-STD 883. In addition, interconnections with silver-containing conductive structures are realized for comparison. Depending on the interconnection system, component mean shear forces of up to 31 N are achieved. While some systems meet the 1.25× criterion of MIL-STD 883, the majority of the systems investigated do not meet the 1.00× criterion. Hereby, the adhesion between the conductive structure and the substrate usually fails. Plasma pre-treatment shows an adhesion-increasing effect only for a proportion of substrate materials used, as does thermal aging. But thermal loads can also impair the adhesive strength.

Surface properties of coated MDF pre-treated with atmospheric plasma and the influence of artificial weathering

A non-thermal plasma treatment generated in air at atmospheric pressure was used for surface modification of medium density fiberboard (MDF) substrate. Untreated and plasma-treated substrates were coated with a waterborne acrylic coating and exposed to accelerated artificial weathering (AAW) in interior mode. Plasma treatment increased the surface free energy of MDF by about 50%, which positively influenced on the wettability of the MDF with the coating. Weathering of the coated MDF caused a decrease in surface gloss and color changes, which were less pronounced for plasma-treated samples. Attenuated total reflection Fourier transform infrared spectra and microscopic analysis revealed degradation of the acrylic resin on the coated MDF due to light irradiation during weathering. After 250 h of weathering, the surface roughness of the coated MDF increased by about 3 μm. The coated MDF surfaces started to lose their hydrophobic character after 50 h of weathering. Finally, the determination of mechanical properties showed that coated MDF became more resistant to scratching during AAW, while the adhesion of the coating film to the MDF substrate was not affected in a significant trend with time of AAW. In both cases, no influence of plasma treatment was detected.

Redox Switchable Polydopamine-Modified AFM-SECM Probes: A Probe for Electrochemical Force Spectroscopy.

Polydopamine (PDA) has high potential in biorelevant applications as a versatile thin film material, e.g., as adhesive coating for cell immobilization or for sensing applications due to the plethora of functional groups. In this study we present the modification of conductive colloidal atomic force-scanning electrochemical microscopy (AFM-SECM) probes with electrochemically deposited PDA resulting in functional probes for quantitative electrochemical adhesion studies. Surface functionality of PDA can be altered by oxidation or reduction of functional groups applying an appropriate potential to the PDA-modified AFM-SECM probe, thereby enabling adhesion measurements under potential control. This facilitates probing specific interactions of surface groups present in PDA with various surfaces of different wettabilities. The versatility of such switchable AFM-SECM probes is demonstrated for electrochemical force spectroscopic studies at model samples such as plasma-treated gold substrates, hydrophobic or hydrophilic self-assembled monolayers, and for adhesion measurements of bacteria in dependence of altered surface charges of the colloidal probe. The maximum obtained adhesion force of a positively polarized PDA-modified AFM-SECM probe was 6.2 ± 2.2 nN, and it was about 50% less (i.e., 2.6 ± 1.1 nN) for a negatively polarized probe at a hydrophilic OH-terminated gold surface. In situ control of the active surface groups enabled investigations on the influence of surface charges on adhesion. Furthermore, plateaus of constant force were observed, which are a characteristic of polymer structures. Finally, electrochemical force measurements with switchable probes were used for the first time during adhesion studies of bacterial cells (i.e., Pseudomonas fluorescens). Positively biased PDA-coated colloidal probes revealed adhesion forces of 6.0 ± 1.1 nN, whereas significantly reduced adhesion forces 1.1 ± 0.7 nN were observed for negatively biased PDA-modified colloidal probes.

Tribological and Electrochemical Characterization of UHMWPE Hybrid Nanocomposite Coating for Biomedical Applications.

A new approach of using a polymer hybrid nanocomposite coating to modify the surface of titanium and its alloys is explored in this study. Electrostatic spray coating process is used to deposit the coating on the plasma-treated substrates for better adhesion. Ultra-high molecular weight polyethylene (UHMWPE) has been selected as the parent matrix for the coating due to its biocompatibility and excellent tribological properties. However, to improve its load-bearing capacity carbon nanotubes (CNT’s) (0.5, 1.5, and 3 wt.%) are used as reinforcement and to further enhance its performance, different weight percent of hydroxyapatite (HA) (0.5, 1.5, 3, and 5 wt.%) are introduced to form a hybrid nanocomposite coating. The dispersion of CNT’s and HA was evaluated by Raman spectroscopy and scanning electron microscopy. The electrochemical corrosion behavior of the nanocomposite coatings was evaluated by performing potentiodynamic polarization and electrochemical impedance spectroscopic tests in simulated body fluid. Tribological performance of the developed hybrid nanocomposite coating was evaluated using a 6.3 mm diameter stainless steel (440C) ball as the counterface in a ball-on-disk configuration. Tests were carried out at different normal loads (7 N, 9 N, 12 N, and 15 N) and a constant sliding velocity of 0.1 m/s. The developed hybrid nanocomposite coating showed excellent mechanical properties in terms of high hardness, improved scratch resistance, and excellent wear and corrosion resistance compared to the pristine UHMWPE coatings.

Acetic-Acid Plasma-Polymerization on Polymeric Substrates for Biomedical Application.

Cold plasma is an emerging technology offering many potential applications for regenerative medicine or tissue engineering. This study focused on the characterization of the carboxylic acid functional groups deposited on polymeric substrates using a plasma polymerization process with an acetic acid precursor. The acetic acid precursor contains oxygen and hydrocarbon that, when introduced to a plasma state, forms the polylactide-like film on the substrates. In this study, polymeric substrates were modified by depositing acetic acid plasma film on the surface to improve hydrophilic quality and biocompatibility. The experimental results that of electron spectroscopy for chemical analysis (ESCA) to show for acetic acid film, three peaks corresponding to the C–C group (285.0 eV), C–O group (286.6 eV), and C=O group (288.7 eV) were observed. The resulting of those indicated that appropriate acetic acid plasma treatment could increase the polar components on the surface of substrates to improve the hydrophilicity. In addition, in vitro cell culture studies showed that the embryonic stem (ES) cell adhesion on the acetic acid plasma-treated polymeric substrates is better than the untreated. Such acetic acid film performance makes it become a promising candidate as the surface coating layer on polymeric substrates for biomedical application.

Effect of Atmospheric Pressure Plasma Treatment on Adhesive Bonding of Carbon Fiber Reinforced Polymer.

To improve the strength of the adhesive-bonded carbon fiber reinforced polymer (CFRP) joints, atmospheric pressure plasma treatment (APPT) was used to treat a CFRP substrate surface. This study investigated the effects of nozzle distance (i.e., the distance between plasma nozzle and CFRP substrate) and nozzle speed (i.e., the moving speed of plasma nozzle relative to CFRP substrate) of APPT on the lap-shear strength of adhesive-bonded CFRP joints. Results show that the lap-shear strength of plasma-treated CFRP joints increased to a peak value and then decreased as the nozzle distance increased, and the nozzle distance associated with the peaked joint strength depends on the applied nozzle speed. The lap-shear strength of plasma-treated adhesive-bonded CFRP joints reaches up to 31.6 MPa, compared to 8.6 MPa of the as-received adhesive-bonded CFRP joints. The surface morphology of plasma-treated CFRP substrates was investigated by scanning electron microscope observation, and the mechanism associated with the improved joint strength after applying APPT was revealed through surface chemistry analysis. It is found that APPT not only effectively removed the content of Si element and –CH3 (i.e., the main compositions of release agent) from the as-received CFRP substrate surface, but also generated many polar groups (i.e., –NH2, –OH, –COOH, etc.), which has a positive effect on increasing the wettability and interfacial bonding strength of CFRP substrates and consequently results in a significant improvement of lap-shear strength of plasma-treated CFRP joints. In addition, the result of differential scanning calorimetry (DSC) test shows that the surface temperature of CFRP substrate should not exceed 175.3 °C during APPT. In this study, an empirical model governing temperature, nozzle distance and nozzle speed was established to guide the selection of atmospheric pressure plasma treatment process parameters in industrial manufacture.

DNA nanostructures doped with lanthanide ions for highly sensitive UV photodetectors.

Deoxyribonucleic acid (DNA) and lanthanide ions (Ln3+) exhibit exceptional optical properties that are applicable to the development of nanoscale devices and sensors. Although DNA nanostructures and Ln3+ ions have been investigated for use in the current state of technology for more than a few decades, researchers have yet to develop DNA and Ln3+ based ultra-violet (UV) photodetectors. Here, we fabricate Ln3+ (such as holmium (Ho3+), praseodymium (Pr3+), and ytterbium (Yb3+))‒doped double crossover (DX)‒DNA lattices through substrate-assisted growth and salmon DNA (SDNA) thin films via a simple drop-casting method on oxygen (O2) plasma-treated substrates for high performance UV photodetectors. Topological (AFM), optical (UV-vis absorption and FTIR), spectroscopic (XPS), and electrical (I‒V and photovoltage) measurements of the DX‒DNA and SDNA thin films doped with various concentrations of Ln3+ ([Ln3+]) are explored. From the AFM analysis, the optimum concentrations of various Ln3+ ([Ln3+]O) are estimated (where the phase transition of Ln3+‒doped DX‒DNA lattices takes place from crystalline to amorphous) as 1.2 mM for Ho3+, 1.5 mM for Pr3+, and 1.5 mM for Yb3+. The binding modes and chemical states are evaluated through optical and spectroscopic analysis. From UV-vis absorption studies, we found that as the [Ln3+] was increased, the absorption intensity decreased up to [Ln3+]O, and increased above [Ln3+]O. The variation in FTIR peak intensities in the nucleobase and phosphate regions, and the changes in XPS peak intensities and peak positions detected in the N 1 s and P 2p core spectra of Ln3+‒doped SDNA thin films clearly indicate that the Ln3+ ions are properly bound between the bases (through chemical intercalation) and to the phosphate backbone (through electrostatic interactions) of the DNA molecules. Finally, the I‒V characteristics and time-dependent photovoltage of Ln3+‒doped SDNA thin films are measured both in the dark and under UV LED illuminations (λLED = 382 nm) at various illumination powers. The photocurrent and photovoltage of Ln3+‒doped SDNA thin films are enhanced up to the [Ln3+]O compared to pristine SDNA due to the charge carriers generated from both SDNA and Ln3+ ions upon the absorption of light. From our observations, the photovoltages as function of illumination power suggest higher responsivities, and the photovoltages as function of time are almost constant which indicates the stability and retention characteristics of the Ln3+‒doped SDNA thin films. Hence, our method which provides an efficient doping of Ln3+ into the SDNA with a simple fabrication process might be useful in the development of high-performance optoelectronic devices and sensors.

Special Issue on Printed Electronics 2017

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Determination of rotational and vibrational temperatures of CH in CH4 plasmas

Understanding fundamental plasma–surface interactions remains an important component of increasing the utility of plasma systems in a range of applications including plasma-assisted catalysis (PAC). A key element in realizing the potential of these applications is understanding the foundational data that control the overall process. Here, fundamental gas-phase and film chemistry trends in methane inductively coupled plasmas are studied to model PAC systems for decomposition of volatile organic compounds. Specifically, energy partitioning trends are presented in conjunction with surface characterization data to elucidate processes occurring at the plasma–surface interface. Optical emission spectroscopy yields rotational and vibrational distribution measurements that can be converted to temperatures (TR and TV) for CH in 100% CH4 and CH4/Ar plasmas as a function of pressure (50–200 mTorr) and applied rf power (25–150 W). Under these conditions, TV ranges from ∼3000 to ∼5000 K, whereas TR has values of 1500–2500 K. These are considerably above room temperature, even at pressures of 200 mTorr and Ar content as high as 25% of total precursor feed. Surface characterization of plasma-treated substrates yields minimal changes in chemical composition but more significant variations in film morphology as functions of plasma pressure and applied rf power. Collectively, these data aim to unravel the complex chemistry of plasma systems for PAC.

Formation and Characterization of Inkjet-Printed Nanosilver Lines on Plasma-Treated Glass Substrates

In this study, we investigated geometrical characteristics of the inkjet-printed lines with non-zero receding contact angle (CA) on plasma-treated substrates in terms of various printing variables and analyzed the fluidic behavior and hydrodynamic instability involved in the line formation process. The printing variables included surface energy, droplet overlap ratio, printing frequency, a number of ink droplets, substrate temperature and printing procedures. For the study, a colloidal suspension containing 56 wt % silver nanoparticles in tetradecane solvent was used as a printing ink. It has electrical resistivity of 4.7 μΩ·cm. The substrates were obtained by performing a plasma enhanced chemical vapor deposition (PECVD) process with C4F8 and O2 under various treatment conditions. As results of the experiments, the surface shape and pattern of the inkjet-printed Ag lines were dominantly influenced by the surface energy of the substrates, among the printing variables. Accordingly even when the receding CA was non-zero, bulging instability of the lines occurred forming separate circular patterns or regular bulges connected by ridges. It is a new finding of this study, which is completely different with the bulging instability of inkjet lines with zero receding CA specified by previous researches. The bulging instability decreased by increasing surface temperature of the substrates or employing interlacing procedure instead of continuous procedure for printing. The interlacing procedure also was advantageous to fabricate thick and narrow Ag lines with well-defined shape through overprinting on a hydrophobic substrate. These results will contribute greatly to not only the production of various printed electronics containing high-aspect-ratio structures but also the improvement of working performance of the devices.

Silver nanoparticles supported on carbon nanotube carpets: influence of surface functionalization

The effectiveness of nanoparticle-based functional devices depends strongly on the surface morphology and area of the support. An emerging powerful approach of increasing the available surface area without decreasing strength or increasing bulk is to attach arrays of suitable nanotubes on the surface, and to attach the necessary nanoparticles to them. Earlier publications by this team have shown that carpet-like arrays of carbon nanotubes (CNTs) can be successfully grown on a variety of larger carbon substrates such as graphite, foams and fabric, which offer hierarchical multiscale supporting architecture suitable for the attachment of silver nanoparticles (AgNPs). A limiting factor of pure CNT arrays in fluid-based applications is their hydrophobicity, which can reduce the percolation of an aqueous medium through individual nanotubes. Previous studies have demonstrated that the treatment of CNT carpets with dry (oxygen) plasma can induce reversible wettability, and treatment with wet (sol–gel) coating can impart permanent wettability. In this paper, we report the influence of such treatments on the attachment of AgNPs, and their effectiveness in water disinfection treatments. Both types of hydrophilic surface treatment show an increase in silver loading on the CNT carpets. Oxygen-plasma treated surfaces (O-CNT) show fine and densely packed AgNPs, whereas silica-coated nanotubes (silica-CNT) show uneven clusters of AgNPs. However, O-CNT surfaces lose their hydrophilicity during AgNP deposition, whereas silica-CNT surfaces remain hydrophilic. This difference significantly impacts the antibacterial effectiveness of these materials, as tested in simulated water containing Gram negative Escherichia coli (E. coli, JM109). AgNPs on silica-coated CNT substrates showed significantly higher reduction rates of E. coli compared to AgNPs on plasma-treated CNT substrates, despite the finer and better dispersed AgNP distribution in the latter. These results provide important insights into different aspects of surface modification approaches that can control the wettability of CNT carpets, and their applicability in water treatment applications.

Quasi-zwitterionic glow-discharge radio frequency plasma coatings

Event Abstract Back to Event Quasi-zwitterionic glow-discharge radio frequency plasma coatings Marvin M. Mecwan1 and Buddy Ratner1 1 University of Washington, Bioengineering, United States Introduction: Glow discharge plasma-treated surfaces have been used to create non-fouling surfaces, and can be readily applied to implants. For successful plasma polymerization it is important that the monomer of interest be easily volatilized. Zwitterionic polymer hydrogels in mice have shown to resist foreign-body reaction[1]. However, zwitterionic polymer precursors, such as carboxybetaine methacrylate (CBMA) and sulfobetaine methacrylate (SBMA) are solids with high boiling points which would not make them ideal candidates for glow-discharge plasma treatment to coat surfaces. This study investigates the preparation of quasi-zwitterionic surfaces via glow-discharge plasma treatment prepared by the simultaneous deposition of a positively charged (N,N-dimethylaminoethyl methacrylate or DMAEMA), and negatively charged (methacrylic acid or MA) monomesr, and may lead to a new generation of non-fouling surfaces. Methods: Silicon substrates were cleaned with methanol in a sonication bath for 10 mins x2. Substrates were allowed to air dry in a chemical hood before plasma deposition. RF-Plasma deposition and delamination: Substrates were loaded into the plasma reactor, and argon etched (40W for 5 min). Using a caliper valve, the monomers of choice—DMAEMA and/or MA—was introduced into the chamber. DMAEMA monomer was heated to 550C and MA monomer was unheated. Plasma deposition was carried out at 250mT pressure; 20W for 30 secs (adhesion) followed by 5W for 15 mins (deposition). Substrates were quenched for 5 mins before venting the chamber and retrieving coated samples. Plasma-treated samples (n=3/group) were washed using DI water x 3 over 24 hrs to assess whether coatings would delaminate. ESCA analyses were done using an S-Probe ESCA (with monochromatic Al K-alpha X-rays focused to 800µm spot size) using survey and detailed C1s scans. Data was analyzed using ESCA analysis software. Results and Discussion: ESCA scans of plasma-treated substrates showed absence of substrate associated peaks (Si), suggesting that coatings did not delaminate. This also implies that plasma coatings on substrates are at least 10 nm thick—ESCA resolution is 100Å (coating thickness will be measured using ellipsometry). Furthermore, experimental and theoretical elemental compositions of the surfaces align well. From the detailed C1s scans for MA coatings we see two distinct peaks at 285.5 and 290 eV associated with hydrocarbon (-CH) and carboxyl (-COO) bonds respectively. For DMAEMA coatings, we see three peaks at 285.5, 287 and 289.5 eV associated with -CH, amine (-NH) and -COO bonds respectively. For the quasi-zwitterionic coatings, we also see three peaks associated with -CH, -NH, and -COO bonds respectively that have been slightly shifted to 286, 287.5 and 290.5 eV respectively when compared to just DMAEMA coatings. This shift can be attributed to the combination of both MA and DMAEMA in the quasi-zwitterionic coatings. Conclusions: The preliminary data demonstrates that quasi-zwitterionic surfaces can be successfully created by the simulataneous deposition of MA and DMAEMA. Ongoing studies include determining the amount of positive vs negative charge on the surfaces via derivitization chemistry, as well as their ability to prevent protein adsorption in order to determine the ability of these quasi-zwitterionic plasma coatings to efficaciously perform as a new generation of non-fouling surfaces. Shaoyi Jiang, PhD

Glow-discharge radio frequency plasma polyether and fluoropolyether coated substrates prevent IgG protein adsorption

Event Abstract Back to Event Glow-discharge radio frequency plasma polyether and fluoropolyether coated substrates prevent IgG protein adsorption Marvin M. Mecwan1* and Buddy Ratner1* 1 University of Washington, Bioengineering, United States Introduction: Protein-based pharmaceuticals present unique challenges in processing, packaging and delivery. All proteins rapidly adsorb to solid surfaces, essentially irreversible, and frequently leads to denaturation or aggregation of the protein. Also, there are concerns with substances from the packaging leaching out and affecting proteins. This study examines fundamental aspects of protein interactions with surfaces, particularly using glow discharge plasma-treated surfaces which can be readily applied to delivery devices, packaging and processing equipment [1],[2] and may lead to a new generation of surfaces effective for protein manufacture, storage and delivery. This research particularly focuses on plasma tetraglyme (TG), acrylic acid (AA), perfluoropropylene (C3F6), and perfluoromethyl vinyl ether (C3F6O) plasma treated glass, stainless steel, and cyclic olefin polymer (COP) substrates and their interaction with IgG. Methods: Glass and COP (8mm φ discs), and 316L stainless steel (7 x 7 mm2) substrates were sequentially cleaned with DCM, acetone, and methanol in a sonication bath for 10 mins x 2. RF-Plasma deposition and delamination: Substrates were loaded into the reactor, and argon etched (40W for 5 min). Using a mass flow controller, the monomer of choice was introduced into the chamber and were plasma deposited. Plasma-treated samples (n=3/group) were washed using DI water x 3 over 24 hours to assess whether coatings would delaminate. ESCA analyses were done using an S-Probe ESCA (with monochromatic Al K-alpha X-rays focused to 800µm spot size) using survey and detailed C1s scans. Data was analyzed using ESCA analysis software. IgG adsorption studies: Bovine IgG was tagged using an ICl method. Plasma-treated samples (n=3/treatment group) were immersed in 0.1mg/mL I-125 tagged bovine IgG solution in 1x cPBS with sodium iodide (cPBSI) for 1 hr. Samples were rinsed with cPBS x 3 and counted for 10 mins using a gamma counter. Cytotoxicity studies: Plasma-coated samples were eluted in complete growth medium for 24 hrs (370C, 5% CO2­ incubator). ~80% confluent NIH-3T3 fibroblasts were exposed to eluates from the plasma coated substrates, and observed over 48 hrs using an inverted microscope. ISO 10993-5 guidelines were used for cytotoxic evaluation. Results and Discussion: ESCA scans of plasma-treated substrates showed absence of substrate associated peaks (such as Fe or Si), suggesting that coatings did not delaminate; also implies that plasma coatings on substrates are at least 10 nm thick (ESCA resolution is 100Å). Furthermore, experimental and theoretical elemental compositions of the surfaces align well. Protein adsorption studies show that tetraglyme and acrylic acid plasma coatings are essentially non-fouling (<2 ng/cm2) as compared to C3F6 and C3F6O plasma coatings which adsorbed proteins in the range of 10-14 ng/cm2. Furthermore, all plasma treated substrates show reduced protein adsorption compared to untreated controls. Moreover, fibroblasts exposed to all plasma coating eluates remained viable after 48 hours. Conclusions: The data demonstrate that plasma-treated polyether and fluoropolyether substrates can create a new generation of surfaces that can be used for contact with protein therapeutic agents.Future studies will be aimed at investigating the strength of bonding of IgG to these surfaces, as well as protein aggregation studies. Winston Ciridon; Xia Dong, PhD