On the mechanical properties of PLC–bioactive glass scaffolds fabricated via BioExtrusion

Our manuscript has been accepted in Materials Science and Engineering C 57 (2015) 288–293.

The paper addresses the mechanical characterization of polycaprolactone (PCL)–bioglass (FastOs®BG) composites
and scaffolds intended for use in tissue engineering. Tissue engineering scaffolds support the self-healing
mechanism of the human body and promote the regrowth of damaged tissue. These implants can dissolve
after successful tissue regeneration minimising the immune reaction and the need for revision surgery. However,
their mechanical properties should match surrounding tissue in order to avoid strain concentration and possible
separation at the interface. Therefore, an extensive experimental testing programme of this advanced material
using uni-axial compressive testing was conducted. Tests were performed at low strain rates corresponding to
quasi-static loading conditions. The initial elastic gradient, plateau stress and densification strain were obtained.
Tested specimens varied according to their average density and material composition. In total, four groups of
solid and robocast porous PCL samples containing 0, 20, 30, and 35% bioglass, respectively were tested. The addition
of bioglass was found to slightly decrease the initial elastic gradient and the plateau stress of the biomaterial
scaffolds.

 

On the thermal properties of expanded perlite – metallic syntactic foam

Our manuscript has been accepted for publication in the International Journal of Heat and Mass Transfer.

The paper addresses the thermal properties of syntactic metal foam made by embedding expanded perlite particles in A356 aluminium matrix. Lattice Monte Carlo (LMC) analyses are conducted to determine the thermal characterization of the foam. For increased accuracy, the complex geometry of the metallic foam is captured by micro-computed tomography imaging. Using the resulting detailed geometric models, the effective thermal conductivity tensor is computed with possible thermal anisotropy taken into consideration. The numerical results are verified by comparison with experimental measurements. To this end, an improved steady-state method is used to correct for thermal contact resistance. Furthermore, the effective heat capacity, average density and thermal diffusivity of perlite – metal syntactic foam are determined.

Free download link valid until September 14, 2015 http://authors.elsevier.com/a/1RQjK44xZnwsq

Diffusion in Tissue Engineering Scaffolds

Our paper “Oxygen diffusion in marine-derived tissue engineering scaffolds” has been accepted for publication in Journal of Materials Science: Materials in Medicine. The paper addresses the computation of the effective diffusivity in new bioactive glass (BG) based tissue engineering scaffolds. High diffusivities facilitate the supply of oxygen and nutrients to grown tissue as well as the rapid disposal of toxic waste products. The present study addresses required novel types of bone tissue engineering BG scaffolds that are derived from natural marine sponges. Using the foam replication method, the scaffold geometry is defined by the porous structure of Spongia Agaricina and Spongia Lamella. These sponges present the advantage of attaining scaffolds with higher mechanical properties (2-4 MPa) due to a decrease in porosity (68-76%). The effective diffusivities of these structures are compared with that of conventional scaffolds based on polyurethane foam templates, characterised by high porosity (> 90%) and lower mechanical properties (> 0.05 MPa). Both the spatial and directional variations of diffusivity are investigated. Furthermore, the effect of scaffold decomposition due to immersion in simulated body fluid on the diffusivity is addressed. Scaffolds based on natural marine sponges are characterised by lower oxygen diffusivity due to their lower porosity compared with the polyurethane replica
foams, which should enable the best oxygen supply to newly formed bone according the numerical results. The oxygen diffusivity of these new BG scaffolds increases over time as a consequence of the degradation in simulated body fluid.

ARC Discovery Project

The ARC Project “High Energy Density – High Delivery Rate Thermal Energy Storage” has been funded:

The intermittency of renewable energy sources will be addressed using new thermal storage media.
Advanced heat transfer modelling and in situ neutron diffraction and imaging will be used to optimise the
microstructure of newly developed miscibility gap thermal storage systems. The new media store energy as
the latent heat of fusion of one phase in a stable, high thermal conductivity inverted microstructure. The high
energy density of the latent heat (0.5-4.5 MJ/L) requires storage volumes as little as 5% of those relying
upon heat capacity and the metal matrix has a hundred-fold greater thermal conductivity than current
systems. A range of such materials will be engineered for concentrated solar thermal and space heating
applications.