Both shape memory alloy and superelastic properties of Nitinol material have attracted substantial attention in a wide range of medical applications. A low-energy Nd:YAG laser joining technique shows a high potential to create large diameter Nitinol endovascular devices that contain complex geometry, because of its versatility and controllability to produce complex geometry. The purpose of this thesis is to investigate the effects of laser joining process parameters regarding the mechanical performance of Nitinol stents. Two new endovascular devices have been fabricated using the optimized laser joining process, which have demonstrated successful device delivery and retrieval
The first device is addressing traumatic vascular injuries which require new endovascular devices to rapidly control the excessive internal hemorrhage in the torso. A retrievable stent graft could regulate the internal bleeding temporarily, as fast as possible with the most feasible performance. The stent graft is manufactured using a substantially long Nitinol backbone and covered selectively based on anatomic measurements, with expandable polytetrafluoroethylene (ePTFE). In this study, designing and manufacturing methods were explored, and their impact on the stent graft performance. Geometric and heat treatment parameters were investigated to show their effect on the radial force of the backbone. The resistance force for retrieval and deployment were measured, and analyzed to be manipulated through ePTFE covering. In vitro measurements for bleeding were measured using swine aorta to show the functionality of the stent graft. Finally, the stent graft showed substantial effectiveness for hemorrhage control in vivo, using a swine model.
The second device is a novel stent graft for abdominal organ perfusion with cardiac flow isolation. In this thesis, the effectiveness of the device design has been validated via the assessment of the device performance. The radial force of stent structure was first numerically analyzed using finite element method, then was quantified experimentally. The blood perfusion parameters were investigated to demonstrate their effect on the blood delivered to the abdominal organs, maintaining the organs healthy for donation. In vivo porcine test results have demonstrated smooth delivery and successful placement of the device showing cardiac flow separation with sufficient strength of Nitinol backbone
