A NEW CONCEPT OF DEDICATED DEPLOYMENT DEVICE FOR STENTS HAVING NEGATIVE POISSON’S RATIO

Abstract

Auxetic stents having negative Poisson’s ratio tend to expand radially as well as longitudinally when unidirectional force is applied. Recently, studies have come up with new designs of auxetic vascular and non-vascular stents which are deployed with commercial balloon catheters. Auxetic stents result in minimal longitudinal elongation when deployed with balloon, hence causing the foreshortening of the stents. This research illustrated a novel deployment device for auxetic stents which will apply force both longitudinally and radially thus causing maximal and effective expansion of auxetic stent. In-silico design of deployment device was made on Pro Engineer Wildfire 5.0. Different parts of device were fabricated by milling and high speed lathe machine. The testing of the device was done using auxetic stents, fabricated by using biocompatible polymer ‘Polyurethane’. To validate the experimental results Finite Element analysis (FEA) of stents was also done. The device functions through an umbrella like mechanism. The length of auxetic stent increases when external hydraulic pressure was applied. Practically, the spokes expanded in response to hydraulic pressure thus expanding the stent radially. The degree of linear expansion in one direction influenced the expansion of auxetic stent in other direction. The device exerted pressure longitudinally on to an auxetic stent and this generated expansion in radial direction as well. Since force is applied and distributed on longitudinal axis which has more number of unit cells and hinges, therefore, more expansion of the auxetic stent is achieved which is not the case when the stent is expanded radially through balloon catheter. Comparative analysis of simulated and practical results demonstrated a good agreement.