Mr. Martin A. Cole Profile

Martin A. Cole

at Univ of South Australia

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Publications (3)

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Proceedings Article | 27 December 2007 Paper

Control over wettability via surface modification of porous gradients

Y. Khung, M. Cole, S. McInnes, N. Voelcker

Proceedings Volume 6799, 679909 (2007) https://doi.org/10.1117/12.759377

KEYWORDS: Electrodes, Silicon, Chemistry, Scanning electron microscopy, Etching, Atomic force microscopy, Infrared spectroscopy, Ozone, Platinum, Semiconducting wafers

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The control over surface wettability is of concern for a number of important applications including chromatography, microfluidics, biomaterials, low-fouling coatings and sensing devices. Here, we report the ability to tailor wettability across a surface using lateral porous silicon (pSi) gradients. Lateral gradients made by anodisation of silicon using an asymmetric electrode configuration showed a lateral distribution of pore sizes, which decreased with increasing distance from the electrode. Pore sizes were characterised using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Pore diameters ranged from micrometres down to less than 10 nanometres. Chemical surface modification of the pSi gradients was employed in order to produce gradients with different wetting or non-wetting properties. Surface modifications were achieved via silanisation of oxidised pSi surfaces introducing functionalities including polyethylene glycol, terminal amine and fluorinated hydrocarbon chains. Surface modifications were characterised using infrared spectroscopy. Sessile drop water contact angle measurements were used to probe the wettability in regions of different pore size across the gradient. For the fluorinated gradients, a comparison of equilibrium and dynamic contact angle measurement was undertaken. The fluorinated surface chemistry produced gradients with wettabilities ranging from hydrophobic to near super-hydrophobic whereas pSi gradients functionalised with polyethylene glycol showed graded hydrophilicity. In all cases investigated here, changes in pore size across the gradient had a significant effect on wettability.

Proceedings Article | 14 December 2006 Paper

Switchable surface coatings for control over protein adsorption

Martin Cole, Marek Jasieniak, Nicolas Voelcker, Helmut Thissen, Roger Horn, Hans Griesser

Proceedings Volume 6416, 641606 (2006) https://doi.org/10.1117/12.696290

KEYWORDS: Proteins, Adsorption, Silicon, Polymers, Ions, Polymerization, Statistical analysis, Interfaces, Semiconducting wafers, Biomedical optics

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Control over biomolecule interactions at interfaces is becoming an increasingly important goal for a range of scientific fields and is being intensively studied in areas of biotechnological, biomedical and materials science. Improvement in the control over materials and biomolecules is particularly important to applications such as arrays, biosensors, tissue engineering, drug delivery and 'lab on a chip' devices. Further development of these devices is expected to be achieved with thin coatings of stimuli responsive materials that can have their chemical properties 'switched' or tuned to stimulate a certain biological response such as adsorption/desorption of proteins. Switchable coatings show great potential for the realisation of spatial and temporal immobilisation of cells and biomolecules such as DNA and proteins. This study focuses on protein adsorption onto coatings of the thermosensitive polymer poly(N-isopropylacrylamide) (pNIPAM) which can exhibit low and high protein adsorption properties based on its temperature dependent conformation. At temperatures above its lower critical solution temperature (LCST) pNIPAM polymer chains are collapsed and protein adsorbing whilst below the LCST they are hydrated and protein repellent. Coatings of pNIPAM on silicon wafers were prepared by free radical polymerisation in the presence of surface bound polymerisable groups. Surface analysis and protein adsorption was carried out using X-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry and contact angle measurements. This study is expected to aid the development of stimuli-responsive coatings for biochips and biodevices.

Proceedings Article | 16 February 2005 Paper

Switchable coatings for biomedical applications

Martin Cole, Nicolas Voelcker, Helmut Thissen

Proceedings Volume 5651, (2005) https://doi.org/10.1117/12.582306

KEYWORDS: Proteins, Adsorption, Plasma, Silicon, Polymers, Biomedical optics, Polymer thin films, Atomic force microscopy, Semiconducting wafers, Natural surfaces

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The control over protein adsorption is of major importance for a variety of biomedical applications from diagnostic assays to tissue engineered medical devices. Most research has focused on the prevention of non-specific protein adsorption on solid substrates. Examples for surface modifications that significantly reduce protein adsorption include the grafting of polyacrylamide, poly (ethylene oxide) and polysaccharides. Here, we describe a method for creating surfaces that prevent non-specific protein adsorption, which in addition can be transformed into surfaces showing high protein adsorption on demand. Doped silicon wafers were used as substrate materials. Coatings were constructed by deposition of allylamine plasma polymer. The subsequent grafting of poly (ethylene oxide) aldehyde resulted in a surface with low protein fouling character. When the conductive silicon wafer was used as an electrode, the resulting field induced the adsorption of selected proteins. Surface modifications were analysed by X-ray photoelectron spectroscopy and atomic force microscopy. The controlled adsorption of proteins was investigated using a colorimetric assay to test enzymatic activity. The method described here represents an effective tool for the control over protein adsorption and is expected to find use in a variety of biomedical applications particularly in the area of biochips.

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