膽管支架在放置人體後，最主要的問題是支架再阻塞的發生，因此需進行二次的內視鏡手術進行治療，但這容易造成病患生命的風險及負擔。因此本研究將進行自潔多層覆膜支架製程的開發，延緩支架再阻塞的發生。
本研究開發製作具有自潔功能的覆膜支架，此覆膜為具有自潔特性的多層可降解薄膜，並搭配具有功能性結構之薄膜層，使薄膜更容易隨結構而裂解脫落。當PLA (polylactic acid)薄膜降解時，附著於覆膜支架內壁的再阻塞物質，會隨著PLA薄膜上的圖形崩解成碎片狀而掉落，達到自潔的功能。
在自潔覆膜中，最重要的是結構薄膜層的製作，本研究分別使用PDMS模具，以及蝕刻PVA的方式進行薄膜結構的製作，並探討製程的可行性。結果發現使用蝕刻PVA薄膜的方式，可用於多種圖形與深度的結構薄膜製作，以及可堆疊製作多層覆膜。本研究使用蝕刻方式在圓柱上進行管狀覆膜結構的製作，以及搭配多層覆膜製程，完成自潔覆膜支架的製作。經實驗驗證自潔覆膜的降解過程分為兩階段，第一階段為表層PLA薄膜的緩慢降解與圖案化裂痕的產生，接著第二階段為隨著下層PVA層的快速降解，表層PLA薄膜裂解成薄膜碎片而掉落，完成覆膜支架的自潔功能。本研究所設計製作的多層覆膜支架可依設計時間間隔進行多次自潔，未來可避免植入後支架再阻塞的發生。

After the biliary stent is placed in the body, the main problem is the occurrence of stent reocclusion. The secondary endoscopic surgery is needed to deal with the reocclusion, but it may cause patients’ life risk and financial burden. This study is trying to develop a multilayer covered self-cleaning stent, with the function of delaying the occurrence of stent reocclusion, and its fabrication process.
This multilayer covered self-cleaning stent consists of a self-cleaning membrane, made up of biodegradable PLA (polylactic acid) films and PVA (polyvinyl alcohol) films with functional structures, and a self-expandable nitinol stent. When the biodegradable films are degraded periodically, sludge attached on the inner wall of stent will drop as the films disintegrate into fragments, and therefore the function of periodic self-cleaning is achieved.
In the built-up procedure of the self-cleaning membrane, the most important and difficult part is the structural layer fabrication. In this study, a casting method with PDMS (polydimethylsiloxane) mold and a PVA film etching method were tried to fabricate the film structures. The results show that the PVA membrane etching method can be used for fabricating a variety of patterns with different depth and it is suitable for fabricating stacking multi-layers. In the following, the etching method was applied to fabricate biodegradable tubular films with designed patterns on a 10 mm diameter round bar, then the tubular films were transferred to a nitinol biliary stent to complete a multilayer covered self-cleaning stent. The self-cleaning membrane degradation process can be divided into two stages: in the first stage the surface PLA thin film degrades slowly and finally patterned cracks are produced on it; in the second stage the PLA film disintegrates into fragments and drops with the quick degradation of the under PVA film, and the function of self-cleaning is achieved. The designed and fabricated multilayer covered self-cleaning stent has been proven experimentally to be able to repeat the self-cleaning process and achieve the function periodically. The developed multilayer covered self-cleaning stent could be used in the future to prevent the stent reocclusion after stent delivery.

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