ABSTRACTS

The following is a list of the abstracts for papers which will be presented in the SEVENTH INTERNATIONAL SYMPOSIUM ON POLYMER SURFACE MODIFICATION The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, FIREFOX, Netscape, ... etc.)

Graft Co-Polymerization of 1, 5 diaminonaphthalene to improve adhesion between EPDM Rubber and Polyester Fabric

EPDM mixes containing different types of bonding materials and various commercialantioxidants were used to evaluate the adhesion of EPDM rubber to polyester fabric.A new antioxidant was prepared by graft copolymerization of 1, 5 diaminonaphthalene (DAN) onto Natural Rubber (NR) in order to investigate itseffect on adhesion. It was observed that EPDM mixes containing the newly prepared DAN shows better adhesion levels than those containing commercial antioxidants. It is also clear that the new system has high resistance towards ageing and ionizing radiation.

Surface Modification of Polyimide Using Atmospheric Plasma for Increasing Adhesive Bond Strength

(Abstract not yet available)

Endothelial Cell Adhesion to Synthetic Vascular Grafts Using Biotinylated Fibronectin in a Dual Ligand Protein System

Endothelial cells mediate the anti-thrombotic activity in healthy blood vessels, and due to the scarcity of suitable autologous vascular replacements, EC-seeded synthetic vascular grafts represent a clear, immediate, and practical solution The objective of these experiments was to optimize a dual ligand (DL) protein system on SVG surrogates to show enhanced cell adhesion, retention, and native functionality compared to fibronectin alone. The first modification, direct biotinylation of fibronectin (bFN), was analyzed with a Langmuir model using surface plasmon resonance (SPR) spectroscopy to verify the binding affinity of bFN and ELISA to detect the availability of RGD post biotinylation. The second change examined cell binding and formation of focal adhesion after shifting from direct incubation of HUVECs with RGD-SA to sequentially adsorbing bFN and RGD-SA prior to introducing unmodified HUVECs. These experiments were conducted under static seeding conditions. Next, we used a dynamic seeding method to examine the initial attachment of perfusing HUVECs to Teflon-AF substrates sequentially adsorbed with biotinylated fibronectin (bFN) followed by RGD-streptavidin mutant (RGD-SA). The dynamic cell seeding studies confirmed that the dual ligand system promotes HUVEC adhesion and retention at short time points. This formulation can be used to augment EC attachment to SVG prior to implantation.

Email: info@dtnw.de

Photo-initiated Inter-Linking of Coatings on Textiles and Other Polymer Substrates

Besides plasma-based processes, photo-initiated surface modifications have an interesting potential for adhesion promotion, which is of special interest with applications ranging from classical finishing to composites. Photo-chemical processes using continuous UV sources - monochromatic as well as broad band - are based on radical activation and ensuing reaction with the atmosphere. Achievable effects are the addition of atoms - e.g. introduction of oxygen (photo-oxidation) resulting in increased surface energy - of grafting of functional groups. Both have a certain potential for adhesion promotion in a physico-chemical way.

Based on the fundamental scheme of these processes - i.e. a photon-initiated radical reaction at the substrate-atmosphere interface -, a direct ?inter-linking? of substrate and coating polymer is presented in this paper. The principle idea is to apply a thin layer of coating polymer on the substrate and irradiate this composite system at certain UV wavelengths. Given a low absorption of the radiation by the thin coating and - at the same time - a high absorption by the substrate, the radiation will penetrate the coating layer and generate radicals at the interface, which induce a cross-linking between the polymers.

As has been shown for the example of polyethylene (PE) coatings on fabrics made of poly(ethylene terephthalate) (PET), extremely high adhesion forces are achieved without any use of additional adhesion promoters. DSC analysis showed for the given example, that besides direct cross-linking between PET and PE - also indicated by adhesion failure analysis -, increased cross-linking of the bulk PE layer occurs.

1) Centre de recherche sur le bois, Université Laval, Pavillon G-H Kruger, Québec (QC), G1K 7PE, CANADA

2) FPInnovations - Division Forintek, 319 rue Franquet, Québec (QC), G1K 4R4, CANADA

Atmospheric Pressure Plasma Treatment on Sugar Maple (Acer Saccharum) And on Black Spruce (Picea Mariana) Wood. Study of Surface Free Energy Using Contact Angle Measurements

In the last few years, wood industry has faced several difficulties (economic crisis, emerging economies, substitution products ...). In the field of finished and semi-finished products, use of plasma technologies could be an interesting solution to increase the added value of industrial production. Although plasma sources are already used in several industries (polymer, textile, electronic, metal), it is a recent technique for wood industry. Literature has shown that the main interest in use of plasma is the surface modification (water repellency, moisture, adhesion properties).

This work presents an exploratory study of the impact of atmospheric plasma generated by different gases (Ar, O₂, CO₂, N₂, Air, and mixtures of these gases) on wood surface. Our interest is focused on adhesion properties. Contact angle measurement is a technique that brings interesting information in adhesion science. Using the dispersive and non-dispersive approach and according to the nature of gases used for plasma, surface free energy is characterized. From these results the work of adhesion can be evaluated in order to demonstrate a correlation with mechanicals tests (pull-off), of surface coatings, done on same plasma modified surfaces.

Exploiting Biomaterial-Tissue Interactions for Effective Medical Device Performance

Every implanted medical device elicits a response by the host organism called the "foreign body response." Generally, the effects are due to local inflammation, but, rarely, systemic immune responses occur. Inflammatory cells drive the local foreign body response which follows a time course that depends on the chemical and physical structure of the material, the locus of the implant and the status of the organism. With long-lasting implants, there is an acute response followed by a chronic response, which generally produces a fibrous capsule that surrounds and "walls off" the device. With degradable implants, the tissue response can be more complicated as the organism responds to volume changes, particle generation and release of soluble molecules. Healing finally resolves with tissue filling and possible scarring at the implant site. In designing the implantable device for optimal performance, it may be desirable to mitigate or stimulate the foreign body response. For example, implanted sensors may require a minimal fibrous capsule at the sensor tip. In contrast, orthopedic implants may benefit bystimulating ingrowth into porous structures. For both strategies, control of activity at the material-tissue interface is required. Design approaches such as surface modification, pharmacologic intervention and controlled resorption are available to achieve the desired performance goals for the implantable devices.

Inline Plasma Processes in Modified Gas Atmosphere for Adhesion Improvement

While adhesion problems on plastic remain an important cause of production losses and consumer complaints, REACH legislation will restrict the use of currently wide spread use of (toxic) primers. Plasma processes are an important environmentally friendly technology for primer replacement. Therefore corona technology is omnipresent in industry today. Since performance of corona systems is limited, VITO developed new plasma processes by using plasma reactors working in modified gas atmosphere. Inline direct or indirect plasma treatment in modified gas atmosphere (e.g. pure nitrogen) results in an increase of polymer surface energy up to 60 dynes/cm (cfr. 45 dynes/cm for corona treatment) as is shown by contact angle measurements. In contrast with conventional corona equipment the acquired activation level is permanent. By injection of chemicals into the plasma, polymer surfaces can be coated or grafted increasing surface energy permanently up to 70 dynes/cm. The combination of modification of gas atmosphere and injection of chemicals allows application of a large range of chemical functionalities onto polymer surfaces, as is shown by XPS measurements. This way, solutions for specific adhesion problems are provided.

Influence of Processing Conditions on the Adhesion Performance of Atmospheric Plasma Polymerized Primer Coatings on Steel

(Abstract not yet available)

Plasma Polymerized Hexamethyl Disiloxane in Adhesion Applications

Hexamethyl disiloxane (HMDSO) is a precursor that has been used in plasma assisted deposition processes for at least 4 decades. Thin films plasma deposited from HMDSO have found applications in many areas of modern technology and have accompanied the developments in microelectronics, microsystems technology, optical coatings and more recently nano-technological processing. As such a great deal is known about the preparation of the these film both on a laboratory as well as on an industrial scale. More recently we have been investigating thin films deposited from HMDSO with respect to their adhesive behavior towards other plasma polymer films as well as to itself for the gluing of silicon-to-silicon (Si-Si) for potential application in microelectronic device and sensor fabrication. This has been triggered by the need to develop adhesion processes and adhesive materials which can easily be applied as ultra thin layers, that can withstand high temperatures (> 200°C) and aggressive media. Plasma assisted deposition techniques allow for the deposition of nm to µm thick films and by careful selection of precursors and deposition conditions will lead to adhesive materials showing these properties. The deposited materials show a significant adhesive strength, they are temperature stable and resistant to aggressive media.

fracassi@chimica.uniba.it

Non Equilibrium Plasma Treatment of Surfaces at Low and Atmospheric Pressure

Atmospheric pressure non equilibrium plasmas, in particular in Dielectric Barrier Discharge (DBD) configuration, attract significant interest also in the field of surface processing of materials, to replace low pressure plasmas since they are characterized by simpler reactor structure, which do not need expensive vacuum chamber and pumping system. The absence of vacuum reduces treatment costs, allows simple integration in most production lines and makes easier the processing of highly outgassing materials. Despite this advantages, high pressure operation for surface processing is characterized by several disadvantages and by several open questions both related to fundamental and practical aspects. Some of the most debated points are the effect of contaminants, i.e. oxygen, nitrogen and water vapour, the influence of substrate composition, the absence of energetic ion bombardment, the possible different reaction paths al low and atmospheric pressure. These and other aspects will be examined in this presentation along with a description of some processes conducted both in low and atmospheric pressure non equilibrium plasmas, with the aim of comparing the state of the art of these two different experimental approaches. In particular, results will be presented on the hydrophobic and hydrophilic treatment of polymers and on the deposition of thin films from fluorocarbon or from organosilicon precursors.

1015 SWITZERLAND

Hot-Embossing: a Novel Technique for the Replication of Superhydrophobic Polymer Samples.

Superhydrophobicity exhibited by some surfaces is a characteristic well known for long [1] that has been studied thoroughly during the last decades. Recently, new properties, such as low wear and bouncing of droplets [2, 3], have been observed leading to new industrial applications [4]. Production of Superhydrophobic (SH) surfaces is nowadays commonly performed in research laboratories (cleanroom processes, use of PDMS, etc…), but the methods are in most cases difficult to transfer to an industrial scale. In the perspective of a direct industrial application, we chose a polymer molding technique already used to produce microfluidic chips or banknotes: Hot- embossing. It allows replication at a large scale of micro- and nanometric features, and thus production of SH surfaces, if hydrophobic polymers such as Teflon are used. We developed a molding setup to fabricate series of micro- and nanostructured polymer samples from Nickel molds. These molds were produced with various techniques used in microelectronics, such as UV and electron beam lithographies and electroplating, in order to control the aspect ratio, shape, spacing and dimensions of the structures. The structured samples were then studied in detail by electron microscopy, atomic force microscopy, and optical microscopy with the aim of improving existing models for superhydrophobicity and, more generally, the knowledge of liquid behaviors on prepared rough surfaces.

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1. Cassie, A.B.D. and S. Baxter, Wettability of porous surfaces. Transactions of the Faraday Society, 1944. 40: p. 546.

2. Quere, D., Wetting and roughness. Annual Review of Materials Research, 2008. 38: p.71-99.

3. Bartolo, D., et al., Bouncing or sticky droplets: Impalement transitions on

superhydrophobic micropatterned surfaces. Europhysics Letters, 2006. 74(2): p. 299-305.

4. Zhang, X., et al., Superhydrophobic surfaces: from structural control to functional application. Journal of Materials Chemistry, 2008. 18(6): p. 621-633.

Interfaces in Biocomposites: Colloid Force Measurements Between Cellulose and Polylactic Acid

Over the last few years, intensive research have been devoted to the exploitation of natural fibres in composite systems not only due to their interesting reinforcement properties, low density, low cost, and biodegradability, but also due to the fact that these materials can be considered as a vector of development of agriculture local resources in emergent countries.

Among these materials, Poly (lactic acid) (PLA)-flax biocomposites are becoming increasingly popular and exhibit all the above interesting properties. Mechanical properties of reinforced biocomposites, such, as flax/poly (lactic acid (PLA) composites, are largely governed by interfacial properties between the two constituents.

In order to characterize their interactions, the atomic force microscopy was adapted to measure interaction forces between a flat polylactic acid surface and a cellulose microbead attached to the end of an AFM tip. Force measurements have shown the importance of capillary forces when experiments were carried out under ambient conditions and allow separating the contribution of van der Waals forces when RH was extrapolated at 0%.

Our results, through the calculation of the Hamaker constant, show that these forces, for the PLA / cellulose / air system, are lower than those obtained for the cellulose / cellulose / air system and hence underline the importance of optimizing the interface between these materials. This has been done from controlled chemical and enzyme treatment of real fibres. This was compared to the results obtained from the reconstruction of a model plant cell wall on cast cellulose flat surfaces. The effect of pectines residues on the measured interactions and potential interdiffusion between amorphous cellulose and PLA was investigated.

1) Leibniz Institute of Polymer Research Dresden, P. O. Box 120 411, D-01005 Dresden, GERMANY

2) Qimonda Dresden GmbH & Co. OHG, Königsbrücker Str. 180, D-01099 Dresden, GERMANY

Surface Functionalization of Silicone Elastomers to Form Permanently Stable Adhesion Joints

Silicone elastomers have a high potential for applications in advanced technologies, e.g. micro-fluidics, soft lithography or microelectronics. However, besides the favorable properties of these polymer materials, such as their excellent flexibility, durability and high thermal and oxidative stability, applications are limited due to their extremely low surface reactivity and surface free energy causing poor adhesion joints. Various surface modification routes were developed to increase the surface free energy of silicone elastomers by introducing reactive functional groups into the polymer surface. As the modification effect obtained by low-pressure plasma or corona discharge treatments is not permanently stable, efforts were focused on concepts to reduce the hydrophobic recovery of modified silicone surfaces.

Our work follows the concept to use surface functionalities introduced by plasma treatments of polydimethylsiloxane (PDMS) layers for a subsequent "grafting-to" procedure with reactive polymers. In this way, reactive functional surface groups can be created on PDMS for further reactions with polymers to form permanently stable adhesion joints. In order to study the effect of these modifications on the surface properties of the PDMS we used a combination of various surface-sensitive characterization techniques including X-ray photoelectron spectroscopy (XPS), contact angle and electrokinetic measurements as well as roughness measurements. The grafted polymers act as a barrier to avoid the surface segregation of low-molecular weight species from the PDMS bulk and thus, no hydrophobic recovery was observed.

We could show that the adhesion between PDMS surfaces, coated as layers onto silicon wafers, and a photo-patternable spin-on epoxy resin coating can be improved considerably by the above described surface functionalization of the PDMS layers.

1) Fraunhofer-Institute for Mechanics of Materials, D-06120 Halle/S., GERMANY

2) Research Institute of Leather and Plastic Sheeting, D-09599 Freiberg, GERMANY

3) Society for the Promotion of Applied Computer Science, D-12489 Berlin, GERMANY

e-mail: Sandra.Guenther@iwmh.fraunhofer.de

In-line Analytical Investigations of Atmospheric Pressure Plasma Processes in Correlation with Surface Analysis

Due to the excellent ability to be integrated in technological processes, atmospheric pressure plasma discharges are an often used tool to modify polymer surfaces. Chemical changes of the outermost polymer surface layers are obtained by this short, intensive plasma treatment [1]. The realization as a dielectric barrier discharge (DBD), often also known as Corona process, is an established technology in the industry for the polymer surface to be activated, functionalized or coated. For specific applications, tailor-made surface properties can be achieved by defined changes in the treatment atmosphere depending on supplied gases, aerosols or also precursors within a carrier gas. Besides the pre-treatment of plastic film sheets by DBD, plasma jet systems are used for special applications, nowadays [2, 3].

One goal of the presented investigations is to compare and evaluate the use of different atmospheric pressure plasma devices in their efficiency concerning the surface activation on different types of polymer surfaces. Additionally, the optical emission spectroscopy (OES) is applied, to study the reactive species in the plasma. The aim here is to find correlations between the reactions in the gaseous phase and the resulting surface properties and evaluate the gained information as a process controlling tool. The surface modification of the different polymer surfaces is analyzed in particular by the determination of the polarity by contact angle measurements. Additionally, X-ray photoelectron spectroscopy (XPS) as well as surface topography methods, such as atomic force microscopy (AFM), are applied to investigate and evaluate the plasma modified surfaces. By means of peeling tests, the adhesion behaviour of the plasma treated polymer surfaces is tested.

1 Kiesow, A.; Meinhardt, J.; Heilmann, A.; Coating 2, p. 4-37, (2004).

2 Förster, S.; Mohr, C.; Surface and Coatings Technology, Vol. 200, p. 827-830, (2005).

3 U. Lommatzsch; Tagungsband - Plasmabehandlung und Plasma-CVD-Beschichtung bei Atmosphärendruck, EFDS, (2007).

F.Guild@imperial.ac.uk

Air-plasma Pre-treatment for Promotion of Thermoplastic

Adhesion

Forced air-plasma pre-treatment has been used for many years to allow printing on thermoplastics including polyethylene and polypropylene. More recently, these processes have been developed to promote adhesion of these materials which are inherently difficult to bond. The effect of forced air-plasma pre-treatment on Polypropylene has been investigated using X-Ray Photoelectron Spectroscopy (XPS), Angle-Resolved XPS (AR-XPS) and Atomic Force Microscopy (AFM). The pre-treatment process is found to induce both surface chemistry changes and topographical changes. The parameters of the pre-treatment process can be optimised from these observations. The pre-treatment process has been used for adhesive bonding of a demonstrator component; a bumper assembly. The adhesively bonded bumpers performed successfully in standard automotive tests. Further measurements of surface energy to investigate the effect of forced air-plasma pre-treatment on both polypropylene and polyethylene have been carried out. The surface energy was determined using Ramé-Hart Goniometry equipment using measurement of contact angles with droplets of water and glycerol. The surface energy was determined prior to surface treatment, immediately after treatment and at various ageing times after treatment in different environments: dry, ambient and saturated. The mechanisms causing the increase in surface energy, thus the potential improvement in adhesion, are now under further investigation.

Technical University of Berlin, Institute of Material Science and Technology, Polymertechnik/Polymerphysik, Fasanen Str. 90, D-10623, Berlin, GERMANY

Improvement of Mechanical Performance of Hybrid Seaweed/Rice Straw Polypropylene Composite: Effect of Maleic Anhydride

Reinforcement by two or more fibers in a single matrix leads to hybrid composites with a great diversity of material properties. It appears that the behavior of hybrid composite is a simply a weighted sum of the individual components so that there is a more favorable balance of properties in the resultant composite material. In the present work different proportion of seaweed (SW) and rice straw (RS) have to be chosen as filler to prepare hybrid polypropylene (PP) composite by injection molding process. Tensile, bending and impact strength of the prepared composites were investigated. Interfacial adhesion and bonding between the filler and PP matrix were also investigated by Scanning Electron Microscope (SEM) analysis. For further improvement the fillers were subjected to pretreated by esterification with maleic anhydride and thereafter prepared hybrid composite and as well as performed the mechanical investigation.

^*Corresponding author: Dr. M. Masudul Hassan, e-mail: msdhasan@gmail.com

¹Home address: Chemistry Department, MC College of National University, Sylhet-3100, Bangladesh

Underwater Plasma and Glow Discharge Electrolysis (Liquid Electrode) for Polymer Surface Modification

Among new types of plasma processes the underwater plasma is one of the most interesting and attractive methods for the functionalisation of polymer surfaces. It is working under atmospheric pressure conditions. The most attractive feature of such plasma solution system is the presence of water thus suppressing any energy excess, as observed using gas plasmas, by transferring all high energy-species of the plasma to the energy level of electrochemical systems in water. This level involves species with moderate energy which can activate polymer surfaces. Moreover, the water predestines the formation of OH groups at polymer surfaces. Hydrogen peroxide addition or the use of the Fenton catalyst increase the yield in OH groups to 25 OH per 100 C.

Another interesting possibility of the underwater plasma is the use of additional chemicals. In such a way the direction of reaction can be adjusted. For example ammonia and bromine were added.

Another general possibility is the plasma polymerization in the liquid phase. A number of simple organic acids and acrylic acid or vinyl sulfonic acid were added. The acids polmerize by fragmentation and recombination processes, however, acrylic or vinyl species to water-soluble more or less regular classic polymers. This underwater plasma was also applied to porous or powdered materials as carbonanotubes or graphite.

The underwater plasma was compared with the glow discharge electrolysis to extract the specific advantages and disadvantages. Application examples were presented. Technical systems are planned.

Dept. of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge, SINGAPORE 119260

E-mail: cheket@nus.edu.sg

Surface Functionalization via Controlled Radical Polymerizations

Functional polymer chains, or polymer brushes, can be covalently tethered to planar, contoured and porous surfaces, as well as to other molecules and macromolecules, by either the "grafting to" or "grafting from" technique. In this work, functionalization of (i) inorganic substrates, (ii) polymers and membranes, and (iv) metals and alloys were carried out via surface-initiated controlled radical polymerizations (CRPs). Stimuli-responsive porous membranes of controllable pore morphology and surface functionality were prepared from block copolymers or via surface-initiated atom transfer radical polymerization (ATRP). Water-dispersible Fe₃O₄ magnetic nanoparticles for magnetic resonance imaging were prepared via solvent-free ATRP of poly(ethyleneglyco) monomethacrylate. Grafting of antibacterial polymers on metal and alloys via surface-initiated ATRP was carried out to inhibit microbially induced corrosion (biocorrosion) in aquatic and marine environments, as well to impart metal implants with permanently antibacterial surfaces. Well-defined multi-block and star-shaped copolymers of controlled block and arm lengths, and exhibiting low in vitro cytotoxicity and good gene transfection efficiency, were prepared via consecutive ATRPs for non-viral gene delivery.

1) Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague, CZECH REPUBLIC

2) Institute of Physiology, Academy of Sciences of the Czech Republic 142 20 Prague, CZECH REPUBLIC

Cytocompatibility of Plasma-treated and Grafted Polyethylene

Polyethylene (PE) was irradiated with inert Ar plasma, and the chemically active PE surface was grafted with polyethyleneglycole (PEG, molecular weight 200, 6000 and 20 000). The composition and the structure of the modified PE surface were studied using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Changes in the surface wettability were determined from the contact angle measured in a reflection goniometer. The changes in the surface roughness and morphology were followed by atomic force microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMC) and their adhesion and proliferation were studied. We found that plasma discharge and grafting lead to dramatic changes in the surface morphology and roughness of PE. In addition, plasma modification of the PE surface, followed with grafting PEG, significantly increased the attractiveness of the PE surface for the adhesion and growth of VSMC.

E-mail: jkenny@unipg.it

Plasma Modification and Surface Functionalization of Biodegradable Polymers for Controlling the Adhesion of Stromal Cells

Effects of oxygen-based radio frequency plasma enhanced chemical vapour deposition (rf-PECVD) on the surface of poly(L-lactide) (PLLA) polymers and the influence thereof on protein adsorption and on bone-cell attachment are reported. Thin films and porous scaffolds based on PLLA polymer were developed, and the role of surface modifications was investigated extensively. PECVD surface treatments were used to modify the surface functionality and to modulate the protein adsorption on the PLLA polymer matrix. In particular, Bovine Serum Albumine fluorescein isothiocyanate (fitc-BSA) conjugate adsorption on patterned surfaces of treated PLLA was analyzed by fluorescence microscopy. Human marrow stromal cells (MSCs) were cultured on scaffolds and cell adhesion and morphology were assessed using fluorescence microscopy.

The results indicate that the PLLA surface became hydrophilic and its roughness increased with the treatment time and it had a dominant influence on the selective adsorption process of the protein. The outcome of the plasma treatment of various PLLA surfaces has been shown to be the up-regulator of the expression of the cell-adhesive proteins and consequently the improvement of cell adhesion and growth. Oxygen-treated PLLA promotes higher adhesion and proliferation of the MSCs in comparison to the untreated samples. Plasma treated PLLA samples show an enhanced affinity for osteoprogenitor cells.

1) Institut für Oberflächentechnik, Technische Universität Braunschweig, Bienroder Weg 53, D-38108 Braunschweig, GERMANY

2) Fraunhofer Institute for Surface Engineering and Thin Films, Bienroder Weg 54 E, D-38108 Braunschweig, GERMANY

Atmospheric-Pressure Plasma Amination of Polymer Surfaces

Using dielectric-barrier discharges (DBDs) in suitable gas atmospheres, appreciable densities of amino groups can be generated on polymer surfaces. The paper begins with a short presentation of recent studies on the mechanism of the process and possible relevant precursor species. A combination of chemical derivatization and quantitative FTIR spectroscopy was applied for the determination of primary amino groups densities introduced on polyolefine surfaces in DBD afterglows in N₂ and N₂+H₂ mixtures.

Owing to the possibility to generate atmospheric-pressure plasmas in sub-mm³ sized volumes, DBD plasmas can be used to modify polymer surfaces area-selectively: Plasma printing can be applied for the achievement of micro-patterned surface modifications, such as hydrophilization / hydrophobization or chemical functionalization. Direct-patterning polymer surface modification processes are of interest for bio-chemical / bio-medical applications as well as for polymer electronics. Two examples will be presented in more detail,

• the area-selective plasma amination of carbon-filled polypropylene (PP/C204) minidiscs to manufacture micro-arrays with peptide libraries utilizing parallel combinatorial chemical synthesis and



• the continuous treatment of polymer foils by reel-to-reel patterned plasma amination for the subsequent electroless copper metallization, leading to a fast and highly efficient process for the manufacture of structured metallizations for flexible printed circuits or RFID antennas.

Surface Modification of Polymer Textiles by Thermally Dried Ozone

(Abstract not yet available)

New Ways of Drawing Metal Films on Polymeric Materials

(Abstract not yet available)

85350 Freising-Weihenstephan, GERMANY

Surface Modification of Polymer Films for Improvement of the Adhesion of Deposited Metal Layers

(Abstract not yet available)

Adhesion Characteristics of Surface-treated Glass/Epoxy Composite with Nano-particle

The surface of glass/epoxy composite material was embedded with nano-particle which was diluted in methyl ethyl ketane (MEK) during curing process to enhance the adhesion strength of the glass/epoxy composite structure. The morphological effect of the nano-particle on the surface of composite was observed using SEM and AFM. The lap shear strength of the glass/epoxy adhesive joints whose adherends were embedded with nano-particle was investigated with respect to the type and amount of embedded nano-particle. Also, the tensile properties of the nano-particle treated glass/epoxy composite were measured to observe the mechanical degradation of the composite due to the MEK. The surface free energies of nano-particle embedded composites were calculated from the van Oss-Chaudh Hury Good equation to correlate the lap shear strength of the adhesive joints with their surface free energies.

From the experimental results, it was found that the nano-particle treatments of the composite adherend improved much the adhesion strength due to the increased surface roughness in nano-scale and surface free energy as well.

E-mail: sean.liu@ars.usda.gov

The Effect of Polymer Surface Modification on Polymer-Protein Interaction via Interfacial Polymerization and Hydrophilic Polymer Grafting

Protein membrane separation is prone to fouling on the membrane surface resulting from protein adsorption onto the surface. Surface modification of synthetic membranes is one way to reduce fouling. We investigated surface modification of polyethersulfone (PES) as a way of improving hydrophilicity of PES surface thereby reducing adsorption of protein. Hydrophilic polymer grafting onto UV/ozone treated PES and grafting through thin film composite using interfacial polymerization were employed to improve hydrophilicity of commercial PES membranes. Poly(vinyl alcohol), polyethylene glycol, and chitosan were chosen as the grafting hydrophilic polymers. Modified PES membranes were characterized by contact angle, FTIR, XPS, and AFM. Contact angles of modified PES membranes were reduced, ranging from 20% to 50% of that of the virgin PES membranes. Tapping mode AFM was used to examine changes in surface topography of modified PES membranes. The PES membranes modified by interfacial polymerization showed lower roughness (ranging from 1.2 nm to 2.0 nm) than that of the virgin PES membrane (2.1 nm) while modified PES by grafting onto ozone/UV treated PES showed elevated roughness (ranging from 7.0 nm to 25.7 nm). The results of these analyses indicated that the PES membranes were successfully enhanced hydrophilically through surface modification.

Fabrication of Metallic Micro/Nano-Structures on Polymeric Substrates by Using Plasma or UV/VUV Treatments, Micro-Contact Printing and Selective Electroless Plating

The development of metallic macro/nano-structures on polymeric substrates has attracted considerable attention over the last decades because of their potential applications in many emerging areas of technology. In addition to the fabrication of conventional electronic devices (printed circuit boards, large-scale integrated circuits), metal-patterned polymeric substrates can indeed be used to implement novel devices such as organic transistors, photonic and optoelectronic components, micro-analytical systems (chemical and biochemical sensor arrays, separation channels in micro/nanofluidics), radio-frequency identification (RFID) tags and so forth.

In the present work, we describe recent results on the fabrication of micrometer and sub-micrometer-scale metal (Ni, Cu, Ag) structures on polymeric substrates (PI, PC,…) by combining several versatile approaches, namely surface modification using plasma or UV/VUV treatments, micro-contact printing (mCP) and electroless deposition (ELD). Plasma or UV/VUV treatments are mainly used to graft the substrate surfaces (inherently chemically inert and non-catalytic for electroless deposition) with specific functionalities on which the chemical species used to activate the surface for electroless deposition are further chemisorbed. More in detail, palladium-based species are chemisorbed on nitrogen-containing groups (case of Ni or Cu ELD), and tin-based species on oxygen-containing groups (case of Ag ELD). In both cases, the selective transfer of the catalytic initiator on the plasma or UV/VUV-treated surfaces is carried out by mCP using a patterned elastomeric stamp. The substrates are then exposed to the electroless plating solution, therefore the formation of adherent patterned metallic features on stamped areas.

Some additional experiments are also carried out using the patterning of homogeneously functionalized or activated surfaces with passivating species. Under these conditions, elecroless metallization only occurs on the non-stamped areas.

The metal/polymer macro/nano-structures obtained from these various approaches are characterized using optical microscopy, scanning electron microscopy (SEM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and atomic force microscopy (AFM).

Advantages and limitations of these approaches are discussed and typical examples (formation of high resolution periodic arrays spreading over large areas and deposition of micro-electrodes exhibiting complex designs) are illustrated.

1) Boston University, Boston, MA

2) University of California Davis, Davis, CA

3) University of Arkansas at Little Rock, Little Rock, AR

Development of Surface Engineered Low Cohesivity Fine Powders for Respiratory Drug Delivery using Dry Powder Inhalers

Respiratory drug delivery (RDD) devices administer therapeutic aerosols via pulmonary airways to treat asthma, chronic obstructive pulmonary disease, cystic fibrosis, emphysema, pulmonary hypertension, and other diseases like TB, lung cancer, diabetes, allergies, viral infections, and osteoporosis. Breath actuated Dry Powder Inhalers (DPI) used for respiratory drug delivery has fundamental limitations. Drug powders used in DPI are mostly in the size range of 0.5 to 5 µm and are cohesive. In most cases, the API fine powder is mixed with a coarse carrier (excipient) powder for improving dispersion efficiency. Breath actuated dispersion of the cohesive powder require turbulent airflow through powder sample so that the aerodynamic drug forces can overcome the inter-particle adhesion forces for efficient aerosolization. While dispersion is improved with a high inhalation rate, but such breath actuation causes a significant loss of the particles in the throat region due to impaction which reduces the actual dose delivered to the small airways of the lung. In the case of asthmatic children and elderly patients, breath actuated DPI does not work well; the aerodynamic shear force applied by the inhalation air flow is often not sufficient to disperse fine particles. Nearly all drug powders and the commonly used carrier powder (Lactose Monohydrate) are hygroscopic. Moisture seeps in through the blister packaging and increases the capillary adhesion forces and decreases dispersion. We report here development of methods for minimizing forces of cohesion of fine pharmaceutical powder for better dispersion and free flowing properties. The experimental methods include minimization of (a) surface energy of the particles, (b) London-van der Waals molecular forces of adhesion, (c) interfacial solid bridge and liquid capillary forces of attraction and (d) electrostatic forces of attraction between particles. Experimetal data on the dispersion properties of the surface engineered powders are presented.

1) Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, 721302 INDIA

2) Department of Biotechnology, Indian Institute of Technology, Kharagpur, 721302, INDIA

Email: sneogi@che.iitkgp.ernet.in

Low Pressure Radio Frequency Plasma Treatment of Polypropylene for Improved Cell Adhesion

Materials used for biomedical applications are required to have suitable surface properties since they depend more on the surface properties than on the bulk properties. Surface properties greatly influence the cell adhesion and its behavior either directly by guiding cell spreading or indirectly by controlling protein adsorption and their structural rearrangement on the material. Modulation of physical and chemical properties of polymers by various treatments can make the substrates adhesive for cells in culture. In this present study, polypropylene surface was modified using helium plasma to improve cell adhesion on its surface. The experiments were run according to the central composite design of response surface methodology to optimize the process conditions. The effect of the process variables RF power, pressure, flowrate and treatment time on surface energy and percentage weight loss were studied through this experimental design. A statistical model relating the process variables and the responses was developed. The improved hydrophilicity through helium plasma treatment was observed from its surface energy data. Changes in surface chemistry and surface morphology were studied by Fourier transform infrared spectroscopy and scanning electron microscopy. Improved cell adhesion on polypropylene treated with helium plasma at the optimum condition, obtained from the statistical design, was observed.

Email: chenkg@nus.edu.sg

Exploiting Natural Biopolymers for Selective Bio-interactivity with Bacteria and Bone Cells in Orthopedic Applications

Orthopedic implants suffer occasional failures as a result of biomaterial-centered infection and/or poor bonding of the implant to bone tissue. Upon insertion, the implant presents a surface for colonization by both the host tissue cells and bacteria which may be present. In the competition for colonization of the implant surface, the probability of successful tissue integration would be greatly enhanced if tissue integration occurs before appreciable bacterial adhesion can take place since once bacterial adhesion has occurred, it is unlikely that tissue cells will be able to displace these primary colonizers. Infection in orthopedic implant surgery remains one of the most dreaded and major complications in orthopedic practice despite the use of modern antibiotic regimes and surgical measures. In this work, we report on the use of two natural biopolymers, silk sericin and chitosan, for tailoring titanium implant surfaces to achieve selective bio-interactivity towards bone cells and bacteria. In the first approach, titanium surfaces were modified with poly(methacrylic acid) followed by immobilization of silk sericin. The methacrylic acid brushes from surface initiated atom transfer radical polymerization significantly reduce the adhesion of the two bacterial strains (Staphylococcus aureus and Staphylococcus epidermidis) tested. At the same time, the immobilized sericin promotes osteoblast adhesion, proliferation, and alkaline phosphatase activity (ALP). In the second approach, the titanium substrates were covalently grafted with carboxymethylated chitosan (CMCS) followed by conjugation with bone morphogenetic protein-2 (BMP-2). Bacterial adhesion on both the CMCS and CMCS-BMP-2-functionalized surfaces was significantly decreased compared to that on the pristine substrates while osteoblast spreading, ALP activity, and calcium mineral deposition were concomitantly enhanced. Such bio-interactive surfaces with these dual functionalities are promising for orthopedic applications.

1) Advanced Engineered Wood Composites (AEWC) Center, University of Maine, Orono, ME 04469, USA

2) Department of Chemical and Biological Engineering, University of Maine, Orono, ME 04469, USA

Quantifying Short Range Adhesion Forces on Wood-Plastic Composites (WPC) Surfaces

Earlier research demonstrated the feasibility of using atomic force microscopy (AFM) to quantify long range adhesion forces arising from wood plastic composite (WPC) surfaces and their components, before and after an energetic treatment (forced atmospheric plasma treatment (FAPT)). These adhesion forces, in the range of 50 to 700nN, corresponded mostly to electrostatic interactions and, regrettably for most WPC surfaces analyzed, it was not possible to observe statistical differences in the adhesion forces measured. In addition to the electrostatic interactions, heat produced during the FAPT treatment appeared to affect the viscoelastic properties of the WPC components, particularly the lubricant, which caused an increase in the interactions between the AFM tip and the surfaces. To reduce both the electrostatic interactions and the viscoelastic property changes, pure water was used as a medium between the AFM tip and the measured surfaces. Making the adhesion force measurements in water rather than air, allowed the quantification of short range adhesion forces (less than 50 nm) and enabled the differentiation between the AFM tip and the individual surface interactions before and after FAPT treatment. The measured adhesion forces indicated that FAPT is more effective on the polypropylene than on the lubricant or coupling agent surfaces.

Self-Assembling of Molecules at the Surface

(Abstract not yet available)

Influence of Moisture on Atmospheric Pressure Plasma Treatment of Fibers and Polymers

(Abstract not yet available)

Plasma Physics Laboratory, National Institute of Physics, University of the Philippines, Diliman, Quezon City 1101, PHILIPPINES

E-mail: jethrosy@gmail.com, hsalapare@nip.upd.edu.ph

Cellular Adhesion Performance of Polytetrafluoroethylene (PTFE) after Surface Modification Using Hydrogen and Oxygen Low-Energy Gas Discharges

The cellular adhesion performance of polytetrafluoroethylene (PTFE) materials is determined using scanning electron microscopy (SEM) of the adhered cells, contact angle measurements, and Fourier transform infrared spectroscopy (FTIR) tests. PTFE samples are irradiated using hydrogen and oxygen low-energy gas discharges using a gas discharge ion source (GDIS) facility with ion energies varied by changing the plasma discharge current (Id) at intervals of 1 mA. Results show that both the hydrogen and oxygen plasma treatments modify the PTFE surface in morphology but only oxygen treatment modified the PTFE in composition. Both treatment exhibited changes in the wettability of the samples at different Id, lower Id improved material hydrophobicity while higher Id resulted in enhanced hydrophilicity. SEM result showed that the cell spread area for hydrophobic surfaces were higher than the hydrophilic surfaces.

1) Centre for Microsystems Technology (CMST)/ELIS, IMEC, Ghent University, Technologiepark 914A, BE-9052 Ghent -Zwijnaarde, BELGIUM

2) Department of Polymer Materials, Ghent University, Krijgslaan 281 S4, BE-9000 Ghent, BELGIUM

Chemical Modification of a Photo Definable Epoxy Resin to Improve Adhesion with Electroless Copper

The rapid evolution of microelectronics industry is translated in a need for higher density substrates with smaller features. In order to fulfill these requirements, one has to minimize the roughness treatment for dielectric materials (to avoid high frequency losses due to skin effect in the conductor). Since surface roughness is one of the key treatments for the improvement of adhesion, chemical surface modification can (over)compensate this loss of adhesion.

In general, epoxy resins contain secondary alcohol groups on the surface. An approach to modify this polymer surface with cyanuric chloride followed by grafting of polyamines is proposed. In this way, increased interaction between protonated amines and Pd/Sn colloids (in acidic water medium) can improve the adhesion with electroless deposited copper.

A detailed analysis and interpretation of the (modified) surfaces using SEM/EDX, ATR-IR, XPS and AFM is presented. Especially the potential of ATR-IR as a characterization method for polymer surfaces will be highlighted.

1) Leibniz Institute for Plasma Science and Technology (INP), F.-Hausdorff Straße 2, 17489 Greifswald, GERMANY

2) Department of Internal Medicine, University of Rostock, Rostock, GERMANY

3) Medical Biochemistry & Molecular Biology, University of Greifswald,

Greifswald, GERMANY

email: schroeder@inp-greifswald.de

Plasma Polymer Coatings for Improved Cell Adhesion to Titanium Surfaces

Thin plasma polymer coatings allow the attachment of chemical functional groups onto material surfaces. These groups modify the adhesion properties of ions, proteins and biomolecules of the extracellular matrix and finally the adhesion and growth of cells after implantation of artificial materials in the human body.

Regarding this, the attachment of amino groups onto titanium, a commonly used implant material, could have beneficial effects. Amino groups are positively charged in aqueous solution at neutral pH and can attract negatively charged biomolecules, which play a key role in the adhesion of osteoblasts as well as human mesenchymal stem cells (hMSC) to the implant surface.

For this purpose, titanium was coated with a microwave plasma polymer made from allylamine (PPAAm) to boost the initial adhesion processes. The process development was accompanied by physicochemical surface analysis like XPS, FTIR, contact angle, SEM, and AFM. Very thin modified layers were created, which are resistant to hydrolysis and delamination. This titanium surface functionalization was found to be advantageous concerning focal adhesion formation of osteoblasts and hMSC and in consequence for differentiated cell functions in vitro. Intramuscular implantation of test samples in rats revealed a reduced inflammation compared to uncoated titanium.

E-mail: ulrike.schulz@iof.fraunhofer.de

Plasma Modification of Polymers for Optical Applications

The decomposition and ablation of polymer material by plasma etching is a well known basic process. On PMMA and some other polymers plasma etching was applied to produce self-organized stochastic surface structures exhibiting antireflective properties. In combination with thin oxide layers deposited before etching the structure formation can be initiated on further materials. Now the structures can be better controlled and optimized for applications in different wavelength ranges.

Sub-wavelength surface structures with antireflective properties are called "moth-eye"-structures because of they have been primarily observed in nature on the eyes of the night-flying moth. In either case antireflective structures perform a gradient of the effective refractive index from the substrate side to the air side. The conditions for antireflection in the visible spectral range can be fulfilled, if small-sized features with a depth of several hundred nanometers are implemented. The structure obtained on PMMA shows a depth of typically 200-400 nm and a distance between the surface features of approximately 70-100 nm. A broadband antireflective effect that is less sensitive to the incident angle of light was achieved. Additional surface functions can be realized by coating the structured surfaces. Combinations of SiO₂ and fluorine-containing layers are useful to obtain super-hydrophobic behavior and to improve the mechanical resistance.

E-mail: eshunko@wintekeo.com

Cleaning And Improving Adhesion of Surfaces by Their Treatment With Excited Nitrogen

An increase of energy of surfaces by their treatment with excited nitrogen is described. Nitrogen dissociation and excitation was provided in plasmas developed in two types of reactors of capacitively-coupled dielectric barrier configurations: coaxial-cylindrical and flat-rectangular. The coaxial-cylindrical type comprised an inner cylindrical electrode encapsulated in a ceramic sheath installed symmetrically inside a cylindrical ceramic tube passing through an annular outer electrode. The flat-rectangular type comprised a ceramic tube of narrow rectangular cross section supplied with two flat electrodes mounted against one another outside of the long parallel walls of this tube. The operating gas, nitrogen, was flowing in completely insulated discharge gaps formed between electrodes (screened by insulators) of the devices with an average velocity of inlet gas of about 7 to 9 m/s, which corresponds to 12 to 15 m/s of afterglow products. Dielectric barrier discharge plasma was excited in the operating gaps by bipolar pulse voltage (applied to the electrodes) of about 6 kV and 2 ms at 60 kHz repetition rate for the coaxial device, and of about 12 kV, 7 ms at 30 kHz repetition rate for the flat linear device. The lifetime of excited nitrogen in certain cases was about 10 ms allowing us to separate the excited medium from the plasma that it produced. It has being shown that the surface treatment process included van der Waals bond liberation as well partial chemical transformation. For example, teflon (PTFE) film surfaces revealed (after treatment) measurable wettability for check-droplets of 30 erg/sm² surface tension.

Adhesion Improvement of Polymers and Glues to Steel Substrates by Various Surface Modifications

(Abstract not yet available)

Selective Chemical Modification of Polymer Surfaces through Low-Energy Ion-Beam Deposition

The reaction of gaseous ions with surfaces occurs as a result of ion-beam deposition at a variety of incident energies and are used for a wide range of applications, including thin-film growth, doping, sputtering, chemical modification, and creation of new interfacial structures. This presentation will focus on the use of several levels of theory to investigate the reactions of gaseous ions with polymer surfaces. In particular, ab initio quantum chemical calculations, density-functional theory molecular dynamics (MD) simulations, and classical MD simulations will be used to examine the selective chemical modification of oligomers with optoelectronic properties, such as sexithiophene and poly(vinylphenylene), through the deposition of ions, such as H⁺, F⁺, C₂H⁺, and C₂F⁺. The incident energies that will be considered are in the range of 1-10 eV. The goal is to determine how gaseous ion reactions with these oligomer surfaces might be used to improve their stability without degrading their optoelectronic properties.

This work is supported by the National Science Foundation (CHE-0809376).

Metal Nanolayers on Plasma Treated Polypropylene

The increasing use of polymeric materials in high technological fields has forced the need to overcome some of their limitations by means of innovative processing. Polypropylene (PP) is frequently being used for industrial automotive applications due to their advantageous properties (good resistance to corrosion) and ability to be readily recycled. Cold plasma treatment represents an efficient, clean and economic alternative to activate polymeric surfaces. The motivation is a rather broad practical use of metal-polymer layers in microelectronics and optoelectronics.

This work deals with characterization of polymer surface and properties of gold nanolayers prepared on pristine and modified PP. We study polymer's wettability, aging of surface and surface morphology. Sheet resistance determines continuity of prepared nanolayers. Surface morphology of metal nanolayers was measured with the respect to the different modification parameters of substrate and thicknesses of layers. Samples were exposed to argon plasma discharge. With increasing time from the plasma exposure the contact angle increases. The aging of PP samples was also studied. Plasma exposure leads to the change of sample's surface morphology, as well as consecutive gold sputtering. The continuity of a gold layer was examined by measuring its electrical resistance. The surface morphology of PP foil also changes with different thicknesses of sputtered gold.

Ion Modifications of Metal/Polymer Interfaces

(Abstract not yet available)

1) Department of Electronics and Photonic System Engineering, Hiroshima Institute of Technology, 2-1-1 Miyake Saeki-ku, Hiroshima 731-5193, JAPAN

2) Laboratory Physical Problems of Electron Beam Technologies, Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko shosse, 1784 Sofia, BULGARIA

3) Department of Surgery, Saitama Medical University International Hospital, 1397-1 Yamane, Hidaka-shi, Saitama, 350-1298, JAPAN

Room Temperature PBII Sterilization of Materials

Recently, the plasma-based ion implantation (PBII) is applied as a sterilization technique at nearly room temperature of samples [1,2].

In our experiments pulsed high negative voltage impulses with amplitude chosen between 0.8 kV and 15 kV, at 5 µs pulse width and frequency of 300 pulses/s is applied to the sample holder (an insulating, from the chamber, electrode) in a N₂ ambient environment at a gas pressure of 2.4 Pa. The used treated samples were from filter material uniformly coated with Bacillus pumilus - the internationally recognized biological standard for irradiation sterilization. The microbiological efficiency of the PBII treatment was characterized by monitoring the number of the B. pumilus population after ion irradiation. Considerable sensitivity of microorganism killing to the used impulse voltage was obtained while noticeable dependence on the ion dose was not observed for the irradiation time more than 5 min (at the mentioned impulse parameters and applied voltage U > 4 kV). Our results show that N_s, the number of survivors after ion irradiation, could be estimated by the relation: lg N_s = 7 - 0.32 U , where U is in [kV], and the ratio N_s/N₀ (N₀ is their initial number) is estimated by: lg (N_s/N₀) = 2.1 - 0.32 U.

Using our computer program TRIM-MV [3] ion ranges are estimated. The energy distribution of irradiating ions was also evaluated [4]. A discussion and comparison concerning calculated ion range distributions and experimental dependences are presented.

The results are encouraging that PBII method could be applied to fast sterilization of unstable at heating or at radiation modification samples (medical or dental materials, powders, tissues, drugs, etc.). The absence of reactive environment is an advantage of the presented method. Nevertheless evaluation of the role of adding reactive gases is possible in future.

References:

[1] T.Tanaka, S.Watanabe, K.Shibahara, S.Yokoyama, and T.Takagi, J. Vac. Sci. Technol. A, 23, 1018-1021 (2005).

[2] T.Tanaka, S.Watanabe, and T.Takagi, Nucl. Instr. and Methods in Phys. Res. Sec. B, 242, 371-373, (2006).

[3] K.Vutova, G.Mladenov, T.Tanaka, and K.Kawabata, Microelectron. Eng., 78-79, 533-539 (2005).

[4] T.Tanaka, K.Vutova, E.Koleva, G.Mladenov, T.Takagi, "Surface modification of plastic films by charged particles", accepted for publication in Polymer Surface Modification: Relevance to Adhesion, Vol. 5, K.L.Mittal (Ed.), VSP/Brill, Leiden, USA, (2009).

1) Department of Chemistry, Center for Materials Science and Engineering, Rochester Institute of Technology, Rochester, NY 14623, USA

2) Department of Physics, RIT, Rochester, NY 14623, USA

3) Xerox Corporation, Webster, NY 14580, USA

Surface Oxidation of Polyimides with UV Photo-oxidation in the Absence of Ozone

Polyimides (PIs) have properties, such as moderate dielectric constant, low permittivity, and flexibility, which make them ideal candidates for the fabrication of thin-film electronic packages of flexible circuitry where the adhesion of metal circuit traces is critical. The PIs, poly(biphenyl dianhydride-para-phenylene diamine) (BPDA-PDA), Upilex-S, and poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA), Kapton HN, were photo-oxidized with UV radiation (254 nm and broad band radiation centered at 300 nm) that is transparent to oxygen molecules. X-ray Photoelectron Spectroscopy (XPS) was used to detect the functional groups in the top 2-5 nm of the sample's surface. Adhesion of sputtered Cu to the modified surfaces was evaluated. The results are compared to our previous studies where 185 nm photons were used to photo-dissociate oxygen molecules and produce ozone to modify the surfaces of BPDA-PDA [1] and PMDA-ODA [2].

[1] U. Sener, B. Parekh, A. Entenberg, T. Debies and G. A. Takacs, J. Adhesion Sci. Technol. 20, 319-334 (2006).

[2] U. Sener, A. Entenberg, B. Kahn, F. D. Egitto, L. J. Matienzo, T. Debies and G. A. Takacs, in: Polyimides and Other High Temperature Polymers, K. L. Mittal (Ed.), Vol. 3, pp. 535 - 552, VSP, Utrecht (2005).

Polymer & Molecular Electronics Group, IMEC, Kapeldreef 75. 3001 - Leuven, BELGIUM

Polymer Adhesion Layers for Ag Layers Deposited in OLED Processing

One of the main targets in ongoing organic electronic research are backplanes for active-matrix displays using organic light-emitting diodes (AM-OLED) whereby top-emitting displays are preferred because of a higher useful emitting area. In our work, we process organic thin-film transistors (OTFT) at low temperatures (<150 °C) on plastic foils (polyethylenenaphtalate, PEN). There are many challenges in the integration of OLEDs with OTFT backplanes on foil. One of them is the interlayer between the OTFT backplane and the OLEDs. For this layer, low-temperature crosslinkable chemical resistant polymers are required, which, on one hand, provide proper electrical insulation of OTFT and OLED devices, and on the other hand can be processed reliably and provide good adhesion to the OLED anode. The commonly-used metals are Mo or Cr, which have a good adhesion on nearly all surfaces and are accepted in display manufacturing plants. However, from the point of reflectivity and therefore light emission efficiency, Ag would be the preferred option. The challenge from the processing point of view is hereby the bad adhesion of evaporated or e-beam deposited Ag on the most surfaces. Standard solutions (like sputtering or Ar-pre-sputtering) can not be accepted, because of resulting surface leakage paths. To address this issue, we tested a variety of low temperature crosslinkable polymers (e.g. SU-8, parylene C) concerning adhesion, roughness, processability and measured the reflectivity of the Ag at different thicknesses. The majority of the tested polymer interfaces could not withstand the Scotch tape test at metal thicknesses beyond 20 nm. By far the best adhesion properties were obtained with parylene C allowing perfectly processed Ag layers with thicknesses up to 100 nm and surface roughness around 1 nm. The origin of the different adhesion properties will be discussed.

1) Institute of Ophthalmology, and Eye Center, Affiliated Second Hospital, College of Medicine, Zhejiang University, Hangzhou 310009, P. R. CHINA

2) Key Laboratory of Macromolecular Synthesis and Functionalization (Ministry of Education), Department of Polymer Science & Engineering, Zhejiang University, Hangzhou 310027, P. R. CHINA

Surface Modification of Artificial Intraocular Lenses with Plasma Techniques

Surface modification of artificial intraocular lenses (IOLs) has been used to improve the biocompatibility and reduce the post-operative complications after cataract surgery. Our group has been dedicated to study the surface properties and cell adhesion performances of the IOLs modified with plasma techniques for years. We modified the IOLs of different bulk materials with low-pressure plasma induced graft polymerization of hydrophilic biocompatible monomers to improve the surface hydrophilicity and antiadhesive performances. They includes poly(methyl methacrylate) (PMMA) IOLs modified with poly(-allyl glucoside), and silicone IOLs with poly(ethylene glycol) and poly(2-methacryloyloxyethyl phosphoryl-choline) (PMPC). Among them, PMPC immobilization causes the IOL surface far more hydrophilic (water contact angle of 36°) and performs even better in resisting the adhesion of platelets, macrophages and lens epithelial cells. Recently we treated the soft hydrophobic acrylate IOLs with argon dielectric barrier discharge (DBD) plasma at atmospheric pressure, which introduced oxygen-/nitrogen-containing polar groups onto the IOLs surfaces. The suppression of cell adhesion was also observed, which may be related to the specific interactions between the adhesion-associated-proteins and the physicochemically changed IOL surface. Moreover, it is common that the water contact angle values and cell adhesion both tend to be almost constant after a certain period of plasma treatment in all of the four cases.

In Situ Microtribology with High Local Resolution on Nano-modified Surfaces on Polymers

(Abstract not yet available)

Atmospheric Pressure Plasma Jets for Surface Treatment and Medical Applications

Compact miniaturized atmospheric plasmas exhibit very promising technological potential for surface treatment. Basically, there are two features which make them unique: (I) the tool-like, small size and light weight plasma generation unit allows fast and almost arbitrary 3D movements and (II) the contracted and comparably cold plasmas allow focused small-spot treatments, even of heat sensitive small size objects with temperature loads to the surface between 35°C and 90°C. Especially in the area of biomedical applications these opportunities triggered significantly increasing research and development of plasma application directly to living objects. Here, an overview of different tailor-made miniaturized atmospheric pressure plasma sources is presented which can be used for specific purposes of surface coating, functionalization and decontamination.

However, the realization of industrial plasma-based decontamination or sterilization technology still remains a great challenge. This is due to the fact that antimicrobial treatment processes needs to consider all properties of the product to be treated as well as the requirements of the complete procedure, e.g. a reprocessing of medical instruments. Here the applicability of plasma-based processes for the antimicrobial treatment on selected, heat sensitive products with special geometries is demonstrated.

Following this, a discourse is given about possible treatment processes and the state of the art in the new field of plasma medicine, i.e. about expected benefits of localized plasma treatment of living tissue for healing purposes.

1) Hahn-Schickard-Institute of Microassembly Technology HSG-IMAT,

Stuttgart, GERMANY

2) University of Stuttgart, Institute of Micro and Precision Engineering, GERMANY

A New Measuring Tool for Determining the Adhesive Strength of Micro Structured Metal Layers and Conductors Directly on Polymer Micro Devices

The miniaturisation of polymer micro devices such as moulded interconnect devices (MID) offers great opportunities for various applications in a broad industrial field. The adhesive strength of the metal layer or conductor track on the polymer devices is an essential quality feature. However, standard test methods like peel test, pull and shear test are not suitable to characterise the adhesive strength directly on the device, in particular when the width of the conductor tracks is only several hundred microns and the thickness less than 20 µm. To overcome the disadvantages of the known test methods, a new measuring tool for determining the adhesive strength directly on the device has been developed at HSG-IMAT. The measuring principle of the tool is based on a micro chisel which is used to peel the conductor from the polymer device. While peeling the track, the required forces are measured by a two-axis force sensor and used to calculate the adhesive strength. Measurements have been performed on ductile copper conductors on FR4 substrates and on brittle copper-nickel-gold tracks on different polymer MID substrates. The results show the capability of the new measuring tool for in-line quality control during the production of polymer micro devices. Within this paper the new measuring tool and its characteristics will be presented. Furthermore, measurement results obtained from conductor tracks on FR4 and MID substrates will be shown and discussed. The results will also be compared to the standard test methods.

Surface Engineering of Microporous Polypropylene Membranes

Surface engineering of polymer membranes embraces those processes, which modify the membrane surfaces to improve their in-service performance. It means 'modifying the surface' of a membrane to confer surface properties, which are different from the bulk properties. The purpose may be to minimize fouling, modulate hydrophilicity/ hydrophobicity, enhance biocompatibility, act as a diffusion barrier, provide bio- or chemical functionalities, mimic biomembrane, fabricate nanostructure or simply improve the aesthetic appearance for the membrane surface. Among various polymer membranes, microporous polypropylene membranes (MPPMs) are hydrophobic and chemically inert, which can induce severe fouling. Therefore, their potential applications in water treatment, bioseparation and biomedical fields are largely limited. Our series studies indicate that surface-engineered MPPMs can achieve controllable separation performance, long-term stability, and even desired functions. Here we summarize a series of strategies to improve the surface hydrophilization, antifouling property, and antibacterial performance for MPPMs. Among them, we find that interfacial crosslinking combined with pretreatment by dielectric barrier discharge plasma at atmospheric pressure is a facile and effective method, which can endow MPPMs with a highly hydrophilic and charged surface. Accordingly, these MPPMs can inhibit the bacteria growing into biofilm on the surfaces, i.e. the so-called antibiofouling. We believe that this approach can also be easily applied to other common commercial hydrophobic membranes, e.g. polyethylene, polyvinylidene fluoride and poly(tetrafluoro- ethylene), to confer new surface properties on them.

Formation of Periodic Structures by Low Temperature Plasma - Proposed Mechanism

The processes of low temperature plasma treatment of polyamide fiber were systemically studied. Ripple-like structures in sub-micron size perpendicular to fiber axis were observed under particular treatment parameters. Suggested explanations were given of the mechanisms that produce the structure after the processes of plasma treatment. The fundamental approach used in modeling was considered the temperature profile of the material during the treatment. The morphological study results showed that the stress-field inside the fiber and the degree of crystallinity are essentially important in contributing to structure formation.

Plasma Treatment of Hydrocarbon Polymers & Post-treatment Dynamics of Surface Polarity

Low energy oxygen plasma treatments of hydrocarbon polymers are often applied to render their surfaces polar, hence adhesion enhancing and hydrophilic. This is to report how oxygen-containing functional groups on the surfaces are formed by such treatments. First, we performed detailed analyses of the oxygen plasma composition relative to the density of electron, O₂⁺ ion and atomic oxygen as a function of oxygen pressure up to 1000 mT. Correlating the etch rate profiles with those of O₂⁺ ion and atomic oxygen densities, with respect to the oxygen pressure, it is concluded that there are two modes of polar groups formation. In a low pressure regime up to about 400 mT, O₂⁺ ion etching is responsible for the formation of oxygen-containing groups on the surfaces. On the other hand, in a pressure regime higher than around 500 mT, atomic oxygen causes the formation of oxygen-containing groups. We then examined the resulting surface polarity changes with time in contact with humid air. The kinetics of the polarity reversal under the storage is monitored via water contact angle, and for long periods of time up to several months. The contact angle changes from zero immediately after the plasma treatment to 60 in 160 days in storage under the controlled humidity. The sample films were then immersed in water at under controlled temperatures for a specified time, and the time profile of the contact angle was monitored again to find that it reproduces the previous profile with a minor variation. The procedure was repeated up to 3 times, and the reversal-recovery mechanism is proposed on the basis of the characterization of the surface groups by X-ray photoelectron spectroscopy (XPS) and sum frequency generation spectroscopy (SFG).