Fabrication and characterisation of microporous titanium

Microporous titanium was fabricated by a special powder metallurgy process and the microstructure and the mechanical properties of the material were characterised by scanning electron microscopy and quasi-static compression. The pore sizes and porosities of the samples are ranged of 10-50 μm and 40-65%, respectively. Macroporous Ti samples with the pore sizes ranged from 500 to 800 μm were also prepared by the similar process for comparison. The microporous Ti exhibits not only a very different deformation behaviour from the macroporous Ti but also lower flow stress than the latter, completely different from those observed in common porous metals.

In vitro behavior of human osteoblast-like cells (SaOS2) cultured on surface modified titanium and titanium–zirconium alloy

In this study, titanium (Ti) and titanium-zirconium (TiZr) alloy samples fabricated through powder metallurgy were surface modified by alkali-heat treatment and calcium (Ca)-ion-deposition. The alteration of the surface morphology and the chemistry of the Ti and TiZr after surface modification were examined. The bioactivity of the Ti and TiZr alloys after the surface modification was demonstrated. Subsequently, the cytocompatibility of the surface modified Ti and TiZr was evaluated via in vitro cell culture using human osteoblast-like cells (SaOS2). The cellular attachment, adhesion and proliferation after cell culture for 14 days were characterized by scanning electron microscopy (SEM) and MTT assay. The relationship between surface morphology and chemical composition of the surface modified Ti and TiZr and cellular responses was investigated. Results indicated that the surface-modified Ti and TiZr alloys exhibited excellent in vitro cytocompatibility together with satisfactory bioactivity. Since osteoblast adhesion and proliferation are essential prerequisites for a successful implant in vivo, these results provide evidence that Ti and TiZr alloys after appropriate surface modification are promising biomaterials for hard tissue replacement.

Sensitivity of deformation twinning to grain size in titanium and magnesium

The impact of grain size on deformation twinning in commercial purity titanium and magnesium alloy Mg–3Al–1Zn (AZ31) is investigated. Tensile tests were carried out for the titanium samples; compression testing was employed for the magnesium specimens. Average values of the true twin length, true twin thickness and the number density of twins were determined using stereology. A key difference between these two materials is that twinning contributes little to the plastic strain in the titanium while it accounts for nearly all of the early plastic strain in the magnesium. In some respects (e.g. volume fraction and number density) the phenomenology of twinning differed between the two materials, while in others (e.g. twin shape and size) both materials showed a similar response. It is found that in both materials, twins span the entirety of their parent grains only for grain sizes less than ∼30 μm. Both the nucleation density per unit of nucleating interface (i.e. grain and twin boundaries) and the aspect ratio of twins scale with applied stress. The impact of grain size on twin volume fraction is modelled analytically.

Multimodal nanostructured titanium using severe plastic deformation

In the present study, multimodal nanostructured titanium was engineered using severe plastic deformation. The multimodal structured titanium exhibits an ultrahigh strength of over 940 MPa and a large failure elongation of 24%. The ultrahigh strength is mainly derived from the nanostructured structures; whilst the exceptional ductility originates from the large fraction of high angle grain boundaries, micro-scale structures, and the non-equilibrium grain boundary configuration. It is worth noting that apart from dislocation slip processes, the formation of deformation twins reduced the effective slip distance and increased the strain hardening capacity via the Hall-Petch mechanism, leading to high ductility of the multimodal structured titanium.

3D fibrous structures as cardiovascular implants

Medical textiles are a highly specialised stream of technical textiles industry with a growing range of applications. A significant advancement has been achieved in surgical products or biomedical textiles (implantable/non-implantable) with the advent of 3D textile manufacturing techniques. Cardiovascular soft tissue implants (vascular grafts) have been a field of interest over decades for use of innovative 3D tubular structures in treatment of cardiovascular diseases. In the field of soft tissue implants, knitted and woven tubular structures are being used for large diameter blood vessel replacements. Advent of electrospinning and tissue engineering techniques has been able to provide promising answers to small diameter vascular grafts. The aim of this review is to outline the approaches in vascular graft development utilising different 3D tubular structure forming techniques. The emphasis is on vascular graft development techniques that can help improve treatment efficacy in future.

Effect of grain size on deformation twinning in a magnesium alloy and commercial purity titanium

This data collection contains several optical microstructure images, EBSD maps and stress-strain curves. The research involves collecting data from samples with different grain sizes at several values of plastic strains to measure some important twinning parameters such as twin volume fraction and number of twins per grain. The aim of this study is to investigate the effect of grain size on deformation twinning behaviour in two hcp metals i.e. commercial purity titanium and AZ31 magnesium alloy.

Design of a miniature UHF PIFA for DBS implants

This paper presents design and simulation of a miniature rectangular spiral planar inverted-F antenna (PIFA) at UHF RFID band (902.75 - 927.25 MHz) for integration in batteryless deep brain stimulation implants. Operation in the UHF band offers small antenna size and longer transmission range. The proposed antenna has the dimensions of 10 mm × 11.5 mm × 1.6 mm, resonance frequency of 920 MHz with a bandwidth of 18 MHz at return loss of -10 dB. A dielectric substrate of FR-4 of εr = 4.5 and δ = 0.018 with thickness of 1.5644 mm is used in this design. The resonance, radiation characteristics as well as the specific absorption rate distribution induced by the designed antenna within a four layer spherical head model is evaluated by using electromagnetic modeling software which employs the finite element method.