Mark Staiger | University of Canterbury/Te Whare Wānanga o Waitaha (original) (raw)

Papers by Mark Staiger

Digital Image-based Elasto-Tomography (DIET) is a novel surface-based elasticity reconstruction m... more Digital Image-based Elasto-Tomography (DIET) is a novel surface-based elasticity reconstruction method for determining the elastic property distribution within the breast. Following on from proof of concept simulation studies, this research considers the motion evaluation and stiffness reconstruction of a soft tissue approximating gelatine phantom. This initial phantom work provides an intermediate stage between prior simulation studies more detailed phantom studies to follow. Reference points on the surface of a cylindrical phantom were successfully tracked and converted into a steady-state motion description. Motion error based mechanical property reconstruction allowed an estimation of the stiffness of the gelatine when actuated at 50 Hz. The reconstructed stiffness compared favorably with independently measured stiffness properties of the gelatine material when experimental assumptions were considered. An experimental noise estimate of 50% was confirmed accurate by comparing experimental motions to simulated motion data with added noise.

The production of bacterial cellulose (BC) has been studied in two different reactor configuratio... more The production of bacterial cellulose (BC) has been studied in two different reactor configurations - a static surface culture and a Rotating Biological Contractor (RBC). We will present the impact of environmental parameters such as pH on the BC physical properties (scanning electron microscopy, water holding capacity and tensile strength). The RBC produces cellulose with less physical layering as observed by naked eye and as observed by the scanning electron microscope. It also allows better control of the environmental parameters such as pH and mixing. Preliminary results indicate that BC produced in static cultures has a higher tensile strength than BC from a RBC controlled at pH 4.0 (26 MPa vs. 15 MPa) but lower water content (52 g{water}/g{cellulose} vs. 130 g{water}/g{cellulose}). Not controlling the pH in an RBC lowered the water content by 11% but dramatically lowered the tensile strength.

Magnesium alloys are used in a variety of structural applications. Currently, there is an increas... more Magnesium alloys are used in a variety of structural applications. Currently, there is an increasing amount of evidence suggesting that magnesium based alloys could have several biomedical applications. There is adequate evidence supporting the viability of magnesium as biodegradable scaffold for bone tissue regeneration. It is crucial that its corrosion rate has to be controlled by alloying. New Mg alloys have been in vitro tested by electrochemical and other methods. The corrosion rates of Mg12Li and Mg1Ca are quite encouraging because are compatible with the time needed for bone tissue regeneration.

Polymer Degradation and Stability, 2009

Polyethersulfone membranes are widely used for ultrafiltration and microfiltration especially in ... more Polyethersulfone membranes are widely used for ultrafiltration and microfiltration especially in the dairy industry, but they are believed to degrade when exposed to the sodium hypochlorite solution that is used to sanitize the processing equipment. Such membranes were ...

Materials Science and Engineering: A, 2004

In the present study, a new multistage torsion test was developed to study the effect of temperat... more In the present study, a new multistage torsion test was developed to study the effect of temperature, solute level and interpass time (IPT) on static strain aging behaviour. The objective of the present work was to study strain aging under conditions closer to actual wire drawing (i.e. large strains, high strain rates and multistage strain aging) using torsional deformation. The torsion test allowed for a rapid, accurate and controlled method to simulate a range of microstructures and the subsequent testing of the metallurgical properties of the material. The multistage torsion test was found to be suitable for the investigation of multistage strain aging in low-carbon steels under conditions of large strain and high strain rate. Major characteristics of the multistage torsion flow stress-strain curves reported for the first time include: (i) pronounced upper yield points and/or strength increments (Y) after each aging step indicative of static strain aging; (ii) high initial work hardening rates, followed by very low work hardening in the presence of Y; and (iii) serrated flow at temperatures of 200 • C and higher indicative of dynamic strain aging. It was found that in general multistage strain aging was detrimental to the ductility of the material. It was also found that strain aging was in itself dependent on the strain aging history of the material, decreasing with increasing prior strain aging.

Materials Characterization, 2010

ABSTRACT A novel preparation technique is described that makes possible grain size analysis of po... more ABSTRACT A novel preparation technique is described that makes possible grain size analysis of polycrystalline NaCl using orientation imaging microscopy via electron backscatter diffraction (EBSD). The preparation methodology is specifically developed to overcome difficulties in preparing microporous NaCl for microscopy. The grain size and crystallographic texture of polycrystalline NaCl samples, prepared via solution pressure and sintered in the range of 650–780°C, were able to be measured successfully with EBSD. The limitations of the preparation technique for EBSD analysis of NaCl are also discussed.

Journal of Materials Science, 2011

Journal of Biomedical Materials Research Part A, 2014

Magnesium and its alloys are intriguing as possible biodegradable biomaterials due to their uniqu... more Magnesium and its alloys are intriguing as possible biodegradable biomaterials due to their unique combination of biodegradability and high specific mechanical properties. However, uncontrolled biodegradation of magnesium during implantation remains a major challenge in spite of the use of alloying and protective coatings. In this study, a hybrid composite structure of magnesium metal and a biopolymer was fabricated as an alternative approach to controlling the corrosion rate of magnesium. A multistep process that combines metal foam production and injection moulding was developed to create a hybrid composite structure that is topologically-ordered in all 3 dimensions. Preliminary investigations of the mechanical properties and corrosion behaviour exhibited by the hybrid Mg-polymer composite structures suggest a new potential approach to the development of Mg-based biomedical devices.

Composites Part A: Applied Science and Manufacturing, 2012

ABSTRACT A new processing method for fibre-reinforced all-cellulose composite (ACC) laminates has... more ABSTRACT A new processing method for fibre-reinforced all-cellulose composite (ACC) laminates has been developed in this work on the basis of a conventional hand lay-up method. Four layers of a man-made cellulosic textile (Cordenka rayon) and four layers of a natural fibre textile (linen), respectively, were impregnated with the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate (BMIMAc). The impregnated layers were heated under pressure for the fibre surfaces to partially dissolve in the IL and to achieve compaction of the single laminae to form a composite. A matrix phase is formed in situ by the regeneration of dissolved fraction of the fibre via solvent exchange.Both textiles could be processed into thick (&gt;1 mm) cellulose laminates. Analysis of the composite microstructure and phase transformations revealed that the dissolution behaviour of the man-made cellulose fibres was better than of the linen textile resulting in a more homogenous fibre–matrix-interphase and therefore better tensile properties.

Composites Part A: Applied Science and Manufacturing, 2014

The high mechanical properties of single-polymer composites based on degradable non-derivatised c... more The high mechanical properties of single-polymer composites based on degradable non-derivatised cellulose, aka all-cellulose composites, have recently captured the attention of researchers. All-cellulose composites possess the intriguing combination of high strength and biodegradability. However, the biodegradation behaviour of all-cellulose composites has so far not been reported. In this work, soil burial experiments were carried out to compare the biodegradation behaviour of all-cellulose composites with conventional biocomposites in order to investigate the end-of-life disposal of this relatively new class of bio-based composite materials. All-cellulose composites are characterised by exceptional biodegradability with mass losses of up to 73% following a soil burial time of 70 days. An investigation of the mechanisms of biodegradation of all-cellulose composites is undertaken for the first time.

This study investigated the durability performance of wood-plastic composites (WPCs) exposed to a... more This study investigated the durability performance of wood-plastic composites (WPCs) exposed to accelerated water submersion, and freeze-thaw cycling conditions. WPCs were made from virgin/ or recycled high-density polyethylene (HDPE) and polypropylene (PP) with pine (Pinus radiata) sawdust through hot-press moulding. Surface colour, flexural properties, dimensional stability, microstructures of interface, and thermal properties of composites were examined after the accelerated freeze-thaw (FT) cycling. It was found that water absorption and thickness swelling after 24 h water soaking of FT weathered composites were increased compared to corresponding control samples for all composite formulations. Flexural strength and stiffness were decreased; however, elongation at break was increased after the FT cycling. Scanning electron microscopy (SEM) images of fractured surfaces of weathered composite samples confirmed a loss of interfacial bonding between the wood flour and the polymer matrix. Differential scanning calorimetry (DSC) analysis showed the decrease in enthalpy and crystallinity of composites as compared to the neat PP and HDPE, with slight decrease in melting temperature. Crystallinity of the FT weathered composites for both virgin polymer (PP and HDPE) matrices increased, however composites with recycled polymer matrices decreased compared to corresponding control samples. These findings are found valid for composites made of both the virgin and recycled plastics.

Journal of Materials Science, 2012

Electrospinning is a process that is used to create nanofibres, which have the potential to be us... more Electrospinning is a process that is used to create nanofibres, which have the potential to be used in many medical and industrial applications. The molecular structure of the raw material is an important factor in determining the structure and quality of the electrospun fibres. In this study, we extracted collagen from a cold water fish species, hoki (Macruronus novaezelandiae), and prepared it in several different molecular formats (native triple helical collagen, denatured whole chains, denatured atelocollagen chains and gelatin) for electrospinning. Low molecular weight gelatin and atelocollagen did not form fibres. Treatment with 1,1,1,3,3,3 hexafluoro-2-propanol or 40% acetic acid denatured collagen molecules into intact a-chains prior to the electrospinning process. When using intact denatured collagen chains, 10% acetic acid was an effective aqueous-based solvent for producing uniform fibres. This information will be useful for the development of a non-toxic, aqueous solvent system suitable for industrial scale-up of the electrospinning process. Our results show that this low imino marine collagen is a suitable biopolymer for producing electrospun fibres.

This paper describes the behaviour and design of the spinning tip, the effect of solution conduct... more This paper describes the behaviour and design of the spinning tip, the effect of solution conductivity and the effect of substrate choice (Stanger et al 2009) on the development of a laboratory scale electrospinning machine from first principles through to commercial production. The need for such a machine grew out of a particular interest in the potential of electrospun biological

Key Engineering Materials, 2002

An inverse template method that relies on the use of a controlled porous spacer material was impl... more An inverse template method that relies on the use of a controlled porous spacer material was implemented to produce periodic magnesium (Mg) foams. Bulk infiltration pressures were varied to determine a processing-property map. The microstructure and mechanical properties of the resulting periodic Mg foams were investigated using optical and scanning electron microscopy (SEM), and compression testing, respectively. SEM was also used to analyze the surface topology of the periodic foams and compare it to the original template material. It was found that the casting pressure has a great effect not only on the success of the infiltration but also the surface roughness and other microstructural features of the foam.

Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (... more Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (PVOH). In order to improve the mass deposition rate and decrease the final fibre diameter salts (NaCl, LiCl, LiBr and LiF) were added to the solution. The aim was to increase the charge density and hence increase the electrostatic forces on the fluid. It was found that with increasing salt concentration the charge density did increase. However the mass deposition rate was found to decrease and the final fibre diameter was found to increase. The decrease in mass deposition rate is explained by considering the concept of a virtual orifice. The increase in the final fibre diameter is explained by considering the charge distribution in the jet when it behaves like a conductor compared to when it behaves like an insulator. Both mechanisms result from the increase in conductivity of the PVOH solution without significantly modifying other solution properties when salt is added.