Employing synchrotron X-ray scattering and microscopy to explore microstructural mysteries in bioresorbable vascular scaffolds.

Crystal structure and morphology dictate the mechanical, thermal, and degradation properties of poly l-lactide (PLLA), the structural polymer of the first clinically approved bioresorbable vascular scaffolds (BVS). New experimental methods are developed to reveal the underlying mechanisms governing structure formation during the crimping step of the BVS manufacturing process. Our research specifically examines the "U-bends" - the region where the curvature is highest and stress is maximised during crimping, which can potentially lead to failure of the device with dramatic consequences on patient life.

Interaction of Poly L-Lactide and Tungsten Disulfide Nanotubes Studied by in Situ X-ray Scattering during Expansion of PLLA/WSNT Nanocomposite Tubes.

In situ synchrotron X-ray scattering was used to reveal the transient microstructure of poly(L-lactide) (PLLA)/tungsten disulfide inorganic nanotubes (WSNTs) nanocomposites. This microstructure is formed during the blow molding process ("tube expansion") of an extruded polymer tube, an important step in the manufacturing of PLLA-based bioresorbable vascular scaffolds (BVS). A fundamental understanding of how such a microstructure develops during processing is relevant to two unmet needs in PLLA-based BVS: increasing strength to enable thinner devices and improving radiopacity to enable imaging during implantation.

Multi-objective optimisation of material properties and strut geometry for poly(L-lactic acid) coronary stents using response surface methodology.

Coronary stents for treating atherosclerosis are traditionally manufactured from metallic alloys. However, metal stents permanently reside in the body and may trigger undesirable immunological responses. Bioresorbable polymer stents can provide a temporary scaffold that resorbs once the artery heals but are mechanically inferior, requiring thicker struts for equivalent radial support, which may increase thrombosis risk.

Modelling the Temperature Dependent Biaxial Response of Poly(ether-ether-ketone) Above and Below the Glass Transition for Thermoforming Applications.

Desire to accurately predict the deformation behaviour throughout industrial forming processes, such as thermoforming and stretch blow moulding, has led to the development of mathematical models of material behaviour, with the ultimate aim of embedding into forming simulations enabling process and product optimization. Through the use of modern material characterisation techniques, biaxial data obtained at conditions comparable to the thermoforming process was used to calibrate the Buckley material model to the observed non-linear viscoelastic stress/strain behaviour. The material model was modified to account for the inherent anisotropy observed between the principal directions through the inclusion of a Holazapfel-Gasser-Ogden hyperelastic element.