Kim Dahong, Kim Taeyoung, Lee Yong-Gu
School of Mechanical Engineering, Gwangju Institution of Science and Technology.
School of Mechanical Engineering, Gwangju Institution of Science and Technology;
J Vis Exp. 2019 Jul 25(149). doi: 10.3791/59746.
Branched vessels, typically in the form of the letter "Y," can be narrowed or blocked, resulting in serious health problems. Bifurcated stents, which are hollow in the interior and exteriorly shaped to the branched vessels, surgically inserted inside the branched vessels, act as a supporting structure so that bodily fluids can freely travel through the interior of the stents without being obstructed by the narrowed or blocked vessels. For a bifurcated stent to be deployed at the target site, it needs to be injected inside the vessel and travel within the vessel to reach the target site. The diameter of the vessel is much smaller than the bounding sphere of the bifurcated stent; thus, a technique is required so that the bifurcated stent remains small enough to travel through the vessel and expands at the targeted branched vessel. These two conflicting conditions, that is, small enough to pass through and large enough to structurally support narrowed passages, are extremely difficult to satisfy simultaneously. We use two techniques to fulfill the above requirements. First, on the material side, a shape memory polymer (SMP) is used to self-initiate shape changes from small to large, that is, being small when inserted and becoming large at the target site. Second, on the design side, a kirigami pattern is used to fold the branching tubes into a single tube with a smaller diameter. The presented techniques can be used to engineer structures that can be compacted during transportation and return to their functionally adept shape when activated. Although our work is targeted on medical stents, biocompatibility issues need to be solved before actual clinical use.
典型呈“Y”形的分支血管可能会变窄或堵塞，从而导致严重的健康问题。分叉支架内部中空，外形与分支血管相适配，通过手术插入分支血管内部，起到支撑结构的作用，使体液能够在支架内部自由流动，而不会被变窄或堵塞的血管阻碍。为了将分叉支架部署到目标部位，需要将其注入血管内并在血管内移动以到达目标部位。血管的直径远小于分叉支架的包围球；因此，需要一种技术，使分叉支架保持足够小以便穿过血管，并在目标分支血管处扩张。这两个相互矛盾的条件，即小到足以穿过和大到足以在结构上支撑狭窄通道，极难同时满足。我们使用两种技术来满足上述要求。首先，在材料方面，使用形状记忆聚合物（SMP）来自我引发从小变大的形状变化，即插入时小，在目标部位变大。其次，在设计方面，使用剪纸图案将分支管折叠成直径较小的单管。所提出的技术可用于设计在运输过程中可压缩并在激活时恢复其功能适配形状的结构。尽管我们的工作以医用支架为目标，但在实际临床应用之前还需要解决生物相容性问题。
