One step multifunctional micropatterning of surfaces using asymmetric glow discharge plasma polymerization

Micropatterning of surfaces with varying chemical, physical and topographical properties usually requires a number of fabrication steps. Herein, we describe a micropatterning technique based on plasma enhanced chemical vapour deposition (PECVD) that deposits both protein resistant and protein repellent surface chemistries in a single step. The resulting multifunctional, selective surface chemistries are capable of spatially controlled protein adhesion, geometric confinement of cells and the site specific confinement of enzyme mediated peptide self-assembly.

Acetylene plasma polymerized surfaces for covalent immobilization of dense bioactive protein monolayers

Smooth polymerized surfaces, suitable for biochemical and biomedical applications, were deposited using a modified plasma enhanced chemical vapour deposition method with acetylene as a reaction precursor. Horseradish peroxidase (HRP) activity assays showed that the protein immobilized on the plasma polymerized surfaces maintained its biological function for a much longer period of time compared to that on uncoated surfaces. The kinetics of HRP attachment to the plasma polymerized surfaces were analyzed using quartz crystal microbalance with dissipation analysis. Spectroscopic ellipsometry and attenuated total reflection Fourier transform infrared spectroscopy were used to determine the thickness and the quantity of the attached protein. The results showed that the plasma polymerized surfaces provided a high density of attachment sites to covalently immobilize a dense monolayer of proteins.

Corrosion properties of plasma-polymerized methylcyclohexane films using electrochemical methods

Three types of methylcyclohexane (MCH) coating were deposited as interlayer dielectrics on copper using plasma-enhanced chemical vapor deposition (PECVD) at three different RF plasma power levels. The coating performance was then evaluated by an electrochemical im pedance spectroscopy (EIS) and a potentiodynamic polarization test in 3.5 wt.% NaCl solution. An atomic force microscopy (AFM) and Fourier transform infrared reflection (FT-IR) spectroscopy were also conducted to analyze the coatings. The MCH coatings showed a lower corrosion rate than the copper substrate in the potentiodynamic tests. The EIS results showed that the corrosion resistance of the coatings increased with an increasing plasma power. Thus, the MCH films with an increasing plasma power improved the corrosion resistance due to the formation of a low-porosity coating, the enhanced formation of C−H, C−C, and C≡C stretching configurations, and the improved smooth surfaces.

New approaches for adding value to paper and other substrates

This paper describes research into three different but interrelated technologies that can add value to commodity printing substrates by taking advantage of developments in synthetic chemistry, materials science and plasma physics. These investigations have been conducted in a Cooperative Research Centre (CRC) in Australia, called CRC Smartprint. Research into ink receptive coatings based on pigments possessing a positive surface charge has led to coatings that display improved resolution and colour saturation compared with silica based formulations. Although silica exhibits a high level of liquid absorption, it has relatively poor affinity for dye molecules contained in ink-jet ink. The second development involves the use of plasma enhanced chemical vapour deposition at atmospheric pressure to change surface functionality with particular emphasis on absorptive and printing properties. Thirdly, the development of a prototype labelling system based on the application of electrochromic conductive polymer to a flexible substrate that responds to electrical stimuli is discussed. Taken together, these three developments illustrate how both impact and non-impact printing technologies can be judiciously used to apply not only improved visual imagery to paper and paperboard, but also have the potential to enable printing of micro-electronic circuitry directly onto packaging materials, or onto labels that will enable a wide range of improved tracking, security and marketing functions to be incorporated cost-effectively into packaged goods in future.

Surface modification for enhanced corrosion resistance using fluid bed reactor chemical vapour deposition (FBR-CVD)

The use of materials with otherwise desirable mechanical properties is often problematic in practice as a result of corrosion. Susceptibility may arise for a number of reasons, including an electrochemically heterogeneous surface or destabilisation of a passive film. These shortcomings have historically been overcome through the use of various coatings or claddings. However, a more robust surface layer with enhanced corrosion resistance could possibly be produced via local surface alloying using a fluidised bed. A fluidised bed treatment allows a surface to be alloyed, producing a distinct surface layer up to tens of microns thick. Surface alloying additions can be selected on the basis of whether they are known or suspected to enhance the corrosion resistance of a particular material, whilst at a minimum, surface alloying likely provides a more electrochemically homogeneous surface. Electrochemical evaluations using potentiodynamic polarisations in NaCl electrolytes have shown chromised plain carbon and stainless steel surfaces have decreased rates of corrosion, decreased passive current densities, and ennobled pitting potentials relative to untreated specimens.

Electrostatically confined plasma in segmented hollow cathode geometries for surface engineering

A segmented hollow cathode (SHC) geometry was used for electrostatic confinement of plasma, and surface engineering treatments were conducted in this arrangement. The assessed processes included plasma nitriding, reactive deposition of sputtered material, and deposition of carbonaceous films by plasma-enhanced chemical vapor deposition with a bipolar pulsed-dc power supply on steel substrates. The treated specimens exhibited uniform surface morphology and deposition layers. Characterization techniques included optical microscopy, scanning electron microscopy with energy dispersive X-ray capability, and X-ray diffraction. The advantages and potential applications of the SHC arrangement are discussed in view of these results.

Continuous low vacuum coating apparatus

An apparatus for continuously forming a thin-film layer of organic or inorganic functional material on one or both sides of a flexible substrate via plasma enhanced vacuum vapour deposition.

Enhanced properties in chemically polymerized poly(terthiophene) using vapour phase techniques

Poly(terthiophene) is an electronically conducting polymer with potential applications in solar energy devices. In the present study a series of poly(terthiophene) (PTTh) films are chemically polymerized (CP) at various temperatures and compared with a novel method of vapour phase polymerization (VPP). Utilizing the thiophene trimer (terthiophene) as the starting material, polymerization is achieved with Fe(III) tosylate. The films are characterized by their Raman and absorption spectra, in addition to differential scanning calorimetry (DSC), optical microscopy, electrochemical impedance spectroscopy (EIS) and four-point probe surface conductivity measurements. From the spectroscopy studies, increased conjugation length of the polymer chains with decreasing temperature or vapour phase polymerization is evident. More surprisingly, DSC results indicate the order of the polymer chains is dramatically enhanced by vapour phase polymerization and the D.C. conductivity is an order of magnitude higher for VPP compared with traditional CP films. Additionally, the optical micrographs reveal a significantly different morphology than the films cast from solution.

Micro-porous nickel produced by powder metallurgy

Micro-porous nickel (Ni) with an open cell structure was fabricated by a special powder metallurgical process, which includes the adding of a space-holding material. The average pore size of the micro-porous Ni samples approximated 30 μm and 150 μm, and the porosity ranged from 60 % to 80 %. The porous characteristics of the Ni samples were observed using scanning electron microscopy (SEM) and the mechanical properties were evaluated using compressive tests. For comparison, porous Ni samples with a macro-porous structure prepared by both powder metallurgy
(pore size 800 μm) and the traditional chemical vapour deposition (CVD) method (pore size 1300 μm) were also presented. Results indicated that the porous Ni samples with a micro-porous structure exhibited different deformation behaviour and dramatically increased mechanical properties,
compared to those of the macro-porous Ni samples.

Mechanical properties of micro-porous metals produced by space-holding sintering

Micro-porous nickel foams with an open cell structure were fabricated by the space-holding sintering. The average pore size of the micro-porous nickel specimens ranged from 30 μm to 150 μm, and the porosity ranged from 60 % to 80 %. The porous characteristics of the nickel specimens were observed using scanning electron microscopy (SEM). The mechanical properties were studied using compressive tests. For comparison, macro-porous nickel foams prepared by the chemical vapour deposition method with pore sizes of 800 μm and 1300 μm and porosity of 95 % were also presented. Results indicated that the ratio value of 6 and higher for the specimen length to cell size (L/d) is satisfying for obtaining stable compressive properties. The micro-porous nickel specimens exhibited different deformation behaviour and dramatically increased mechanical properties, compared to those of the macro-porous nickel specimens.

Conductive poly(α,ω-bis(3-pyrrolyl)alkanes)-coated wool fabrics

Cross-linked poly(α,ω-bis(3-pyrrolyl)alkanes) were directly applied to woven wool substrates by either chemical, vapour or mist polymerization methods. Choice of dopant could greatly improve the surface resistance. The optimum coating on textiles with the lowest surface resistance, highest colour-fastness and stability was achieved using a mist polymerization method with 1,8-bis(pyrrolyl)octane, iron(III) chloride (FeCl₃) as the oxidant and p-toluene sulfonic acid sodium salt (pTSA) as the dopant.

Adhesion of polymers

Most industrially applied polymer resins and composites have low surface free energy and lack polar functional groups on their surface, resulting in inherently poor adhesion properties. A strong research momentum to understand polymer adhesion in the last decade has been motivated by the growing needs of the automotive and aerospace industries for better adhesion of components and surface coatings. This paper reviews the recent research efforts on polymer adhesion with a special focus on adhesion mechanisms. It starts with an introduction to adhesion with explanatory notes on adhesion phenomena. Recent research on the adhesion mechanisms of mechanical coupling, chemical bonding and thermodynamic adhesion is then discussed. The area of adhesion promoters is reviewed with the focus on plasma and chemical treatments, along with direct methods for adhesion measurement. The topics of polymer blends and reactive polymerization are considered and the interactions with adhesion mechanisms are reported. The concluding section provides recommendations regarding future research on the contentious aspects of currently accepted adhesion mechanisms and on strategies for enhancing polymer adhesion strength.

Order–disorder transitions in poly(3,4-ethylenedioxythiophene)

The commonly held perception that high conductivity in conducting polymers is linked to a high level of π-stacking order in the material is shown here to be of lesser importance in highly conducting poly(3,4-ethylenedioxythiophene) (PEDT), which has been prepared by chemical vapour phase polymerisation. Despite the fact that there is a highly energetic phase transition about 130 °C (110 J/g), and that this transition corresponds to a loss of the long-range π-stacking as observed in grazing angle XRD, the conductivity remains unchanged beyond the transition and only decreases by a factor of two when heating to above 200 °C. The XRD data suggest that order in two dimension remains above the phase transition measured by DSC and this order is sufficient to maintain a high level of electronic conductivity. Furthermore, as the ligand on the iron salt used in the synthesis is varied, the conductivity of the PEDT varies over two orders of magnitude. These phenomena cannot be explained by different degree of doping or crystallinity and it is proposed that the iron salt has an ordering effect during the vapour phase polymerisation.

Surface alloying of metals using fluid bed reactor

The use of fluidised bed reactors for surface alloying is reviewed. Research at Deakin has includes the use of chemical vapour deposition to form chromium rich layers on ferrous substrates, including stainless and tool steel grades. These layers can be modified to carbide or nitride if required by the end application. The deposition of aluminium and silicon has also been successfully achieved.

Achieving a chromium rich surface upon steels via FBR-CVD chromising treatments

Surface alloying via fluidised bed reactor (FBR) chemical vapour deposition (CVD) can be used to produce adherent and highly corrosion resistant surface layers. In this work, 304, 316, and 409 stainless steels and 1020 steel were chromised, producing distinct surface layers tens of micrometres thick. The composition and surface of these layers was characterised using microscopy, GDOES, and XPS. Surfaces were highly enriched in Cr and displayed improved corrosion resistance as determined by electrochemical evaluations. This work demonstrates that it is possible to form continuous, functional and corrosion resistant Cr-rich surface layers via FBR-CVD on a variety of steels.