Influence of Negative Poisson's Ratio on Stent Applications

Stents are usually defined as small tubular structures that are inserted into the diseased region which provide mechanical support of damaged artery or some other hollow organ to restore lumen and blood flow conditions in arteries. Recently developed stents may accumulate functions; for example, they can be used for drug delivery or for treatment of bleeding esophageal varices. Further clinical failures such as crushing, removing, restenosis are some of the most serious reasons for continuing stent improvements. Therefore, our research study has the design and manufacture of an auxetic structure with enhanced mechanical properties through the tailored negative Poisson’s ratio, and its configuration as an auxetic stent to be used for example in the palliative treatment of esophageal cancer and for the prevention of dysphagia as the main objective. Background: The use of stents for esophageal diseases has evolved greatly over the past 30 years. Esophageal cancer is the growth of cancer cells in the esophagus tube which usually originates in the inner layers of the lining of the esophagus and grows outward. In time, the tumor can obstruct the passage of food and liquid, making swallowing painful and difficult. Since most patients are not diagnosed until the late stages of the disease, esophageal cancer is associated with poor quality of life and low survival rates. Method: This research study is organized in three parts devoted to fabrication of auxetic structure and stent samples, experimental testing and discussion of results. For this purpose a model of an auxetic rotating-square geometry with a circular hole structure is developed by laser cutting apolyurethane sheet. The auxeticoesophageal stent was made by folding and gluing the auxetic sheet (with rigid squares and circular holes) into a cylindrical shape. Combined videoextensometry with compressive and tensile testing are employed to determine the deformation response of the auxetic sheet and stent to obtain stress-strain curves and estimation of Poisson’s ratio.Conclusions: The stenting outcomes are improved through mechanical design with tailored negative Poisson’s ratio through cell geometry of the esophagus stent. Theauxetic stent geometry of rotating squares with circular holes will be lighter in weight; reduces obstruction and food impaction because of its unique deformation mechanism; and can reduces migration of the implant stent by embedding inside the tissue.