Stents are scaffold structures that are implanted in body vessels to keep them open. As the image on the front cover illustrates, the use of these biomedical devices can range from supporting blocked arteries in patients suffering from artery stenosis to supporting gullets in patients suffering from oesophageal cancer. The ability of these biomedical devices to fulfil their purpose relies heavily, amongst other things, on how they mechanically behave when they are infl ated and bent to fi t within the vessels. Some of these mechanical aspects are explored in the work by Attard, Gatt and Grima et al. using techniques normally applied to model auxetic structures. The paper on pp. 321–327 shows that with appropriate corrections, the existent models based on simple rotating rigid units can be used to predict the properties of more complex auxetic systems such as the oesophageal stent devices proposed by Ali and Rehman based on the rotating squares model by Grima and Evans. In the paper on pp. 328–337, stents based on hexagonal honeycomb geometries are analysed in terms of their expandability, foreshortening, dogboning and conformability. These effects may have a huge impact on the performance of a stent. The work highlights that, although particular geometries may perform very well in certain aspects, they may perform less well in others.
This work has been funded by the Malta Council for Science and Technology through the R&I-2011-024 (Smart Stents) project awarded to the University of Malta, HM RD Ltd. part of the Velsud Group, and Tek-Moulds Precision Engineering Ltd.