Plasma immersion ion implantation (PIII) is used here to improve the surface bioactivity of polyether ether ketone (PEEK) by modifying the chemical and mechanical properties and by introducing radicals. Modifications to the chemical and mechanical properties are characterised as a function of ion fluence (proportional to treatment time) to determine the suitability of the treated surfaces for biological applications. Radical generation increases with treatment time, where treatments greater than 400 seconds result in a high concentration of long-lived radicals. Radical reactions are responsible for oxidation of the surface, resulting in a permanent increase in the polar surface energy. The nano-scale reduced modulus was found to increase with treatment time at the surface from 4.4 to 5.2 GPa. The macromolecular Young’s modulus was also found to increase, but by an amount corresponding to the volume fraction of the ion implanted region. The treated surface layer exhibited cracking under cyclical loads, associated with an increased modulus due to dehydrogenation and crosslinking, however it did not show any sign of delamination, indicating that the modified layer is well integrated with the substrate – a critical factor for bioactive surface coatings to be used in-vivo. Protein immobilisation on the PIII treated surfaces was found to saturate after 240 seconds of treatment, indicating that there is room to tune surface mechanical properties for specific applications without affecting the protein coverage. Our findings indicate that the modification of the chemical and mechanical properties by PIII treatments as well as the introduction of radicals render PEEK well suited for use in orthopaedic implantable devices.
Zirconium-based alloys are promising materials for orthopedic prostheses due to their low toxicity, superb corrosion resistivity, and favorable mechanical properties. The integration of such bio-implantable devices with local host tissues can strongly be improved by the development of a plasma polymerized acetylene and nitrogen (PPAN) that immobilizes bio-active molecules. The surface chemistry of PPAN is critically important as it plays a key role in affecting the surface free energy that alters the functionality of bio-active molecules at the surface. The cross-linking degree of PPAN is another key property that directly influences the water-permeability and thus also the stability of films in aqueous media. In this study we demonstrate that by simply tuning the zirconium bias voltage, control over the surface chemistry and cross-linking degree of PANN is achieved.
The construction of transparent electronic devices based on zinc oxide depend on the availability of high performance p
type ZnO. This paper addresses the origin of n type conductivity in undoped ZnO which would require compensation
before p-type material is possible. ZnO films were prepared by magnetron sputtering and filtered cathodic arc deposition
with and without PIII. The intrinsic free carrier properties of have been analyzed by infrared ellipsometry and
temperature dependent conductivity measurements. The correlation of intrinsic carrier density and the crystal size and
orientation as assessed by XRD shows that the free carriers originate from charged intrinsic defects. Even an undoped
ZnO film with large and well oriented grains can exhibit substantial defect conductivity. Temperature dependent
conductivity measurements lead to the conclusion that the charged defect sites give rise to electronic subbands in the
band gap. The defect conductivity of undoped ZnO is comparable to values in the literature for Al-doped ZnO.
In many large and small scale devices metal and glass are used side-by-side. In general, metal components are coupled directly to glass components to provide extra strength. However, in certain configurations the metal-glass interface is a structural weak point. This is particularly the case when the composite metal-glass systems are subjected to impact loading. In this work the impact, and subsequent failure, process of a simply layered glass-metal-glass composite structure was investigated. The structure consisted of a core array of cylindrically shaped metal separators sandwiched between two flat sheets of soda-lime glass. High speed photography was used to capture the impact process, and the subsequent failure, of the composite. Even though significant damage was sustained at the impact point, the high speed photography showed that the initial failure point was not at the impact point.
The design and fabrication of biomedical tools using techniques common in microelectronics is becoming established procedure. In our research, we use gaseous plasma dry etching to form microstructures on silicon wafers. These are intended for use in capturing and binding antibodies and live cells in an array to be used in High Throughput Screening (HTS) and High Content Screening (HCS) of new pharmaceuticals. We call this new arraying plate the "Nanotiter" plate. The benefit of our design (100 x 100 wells in a 25 x 25 mm array) over current 96-, 384- and 1056-well microtiter plates are that the number of samples (wells) that can be tested in one plate scan can be substantially increased, the wells can be rapidly and effectively washed, and the well surfaces can be modified to modulate ligand binding. Simple crowding of wells on a plate can result in cross contamination of samples in adjacent wells during the washing. Furthermore, motile cells may migrate between the wells. 1056 microtiter plates currently cannot be washed, and washing 384 plates is problematic. Our design incorporates plasma-deposited polymers that functionally bind antibodies (or other proteins) in but not between wells. Furthermore, the wells can be shaped to minimize cell migration. Inverting the plate on a wash solution allows unbound cells to simply fall away under gravity thus minimising the contamination of adjacent wells. Thus, our Nanotiter plate represents a substantial improvement over existing technology.
Controlling the interaction of surfaces with macromolecules, such as proteins and antibodies, is the key to producing biocompatible prosthetic devices, biosensors and diagnostic arrays. The development of technologies to control these interactions will result in the early detection of disease and have the potential to dramatically reduce costs associated with clinical treatment. For example, tethering functional anti-bodies to a surface in a patterned array allows the selection of specific proteins from a microlitre serum sample, immediately identifying diseases, well before the
symptoms are manifested. Unfortunately, simple physical absorption of proteins onto most surfaces results in changes in their structure and loss of function. The use of ions from plasmas allows flexibility in surface modification by accessing a variety of ion energies and activated chemical species. In this paper we describe plasma based techniques which are being developed to modify the chemistry and morphology of surfaces in order to optimise their interaction with
biomolecules. Early results of plasma processes to activate surfaces for non specific attachment of proteins by hydrophilic /hydrophobic interactions are presented, with particular attention to the time stability of such treatments, which is of special interest.