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The suitability of high temperature techniques was investigated by finite element analysis modelling to give a qualitative view of how the thermal picture develops under a diamond indenter without controlled heating of the diamond. In the case of a low-conductivity sample such as fused silica, the thermal gradient below the indenter tip is relatively diffuse, whereas with a high-conductivity sample such as gold, most of the sample is able to equilibrate at the set temperature, leading to a very steep thermal gradient in the volume of material that must accommodate the deformation. However, in both cases indentation is occurring in material that is at a lower, and unknown, temperature than the bulk sample. The results of the model are validated by comparing results obtained by heating the indenter either indirectly by contact with the sample or utilising a separate heater for the indenter (an isothermal contact method). Nanoindentation results are presented for experiments using a cubic boron nitride Berkovich indenter on both fused silica, at temperatures up to 600°C, and annealed gold at temperatures up to 300°C. Indentation without separate indenter heating tended to produce unacceptable thermal perturbation in the system, whereas the isothermal contact method maintained acceptable thermal drift and produced values of modulus and hardness that compared well with those in the literature. [ABSTRACT FROM AUTHOR]

Cardiac tissue engineering is focused on obtaining functional cardiomyocyte constructs to provide an alternative to cellular cardiomyoplasty. Mechanical stimuli have been shown to stimulate protein expression and the differentiation of mammalian cells from contractile tissues. Our aim was to obtain a flexible scaffold which could be used to apply mechanical forces during tissue regeneration. Poly(1,8-octanediol-co-citric acid) (POC) is an elastomer that can be processed into scaffolds for tissue engineering. We investigated the effect of modifying the porosity on the mechanical properties of the POC scaffolds. In addition, the effects of the storage method and strain rate on material integrity were assessed. The maximum elongation of POC porous films varied from 60% to 160% of their original length. A decrease in the porosity caused a rise in this elastic modulus. The attachment of HL-1 cardiomyocytes to POC was assessed on films coated with fibronectin, collagen and laminin. These extracellular matrix proteins promoted cell adhesion in a protein-type- and concentration-dependent manner. Therefore, POC scaffolds can be optimised to meet the mechanical and biological parameters needed for cardiac culture. This porous material has the potential to be used for cardiac tissue engineering as well as for other soft tissue applications.