血管支架之製造：雷射與拋光

Abstract

心血管支架為一項微型醫療器材，於施行氣球擴張術後，將血管支架部署於血管中，以其徑向強度維持血管管徑。目前血管支架手術已成為心血管疾病的主要治療方式，並提供其他周邊血管病變治療新的選擇。而目前心血管支架主要的製造方式是利用雷射在中空微管上進行切削，再透過進一步的電化學拋光，改善其表面品質。本文即是對雷射其中幾項重要的參數進行測試，分別找出適合不鏽鋼、鈷鉻及鎳鈦三種不同管材的雷射加工參數，切出結構完整的支架，再將切出的支架進行拋光參數的測試並做拋光前後的比較。在雷射部分測試了實驗室雷射機台的聚焦位置、三種材料的雷射功率範圍以及輔助氣體氣壓對於切割品質的影響。拋光部分則對三種材料進行拋光時間以及拋光電流的探討。利用線寬的量測，找出了實驗室雷射機台的雷射光束聚焦於距離雷射出口3.6 mm的地方，並且得到適合加工的雷射焦深約為0.16 mm;也發現雷射功率對於線寬的影響不大，不因雷射功率的增加而有大幅度的改變。而實驗結果也發現，輔助氣體若不夠大，則在切割邊上亦留下熔渣，甚至導致除去的區塊無法脫離，就不鏽鋼而言，氣壓大於12 bar 時，才能有較好的切割品質。拋光的實驗則顯示，隨著拋光時間增加，平均支架寬度將呈現線性的減少；增大電流則會增加拋光的侵蝕速度。並且透過支架各部位寬度的量測發現，整個支架在拋光過程中會均勻的變細，侵蝕速度不會因為部位不同而有明顯的差異。對於三種不同的管材，已找到各自適合的雷射參數足以切出結構完整的支架，也確定了文中拋光液的成分與拋光流程的操作確實可以達到拋光的效果。此研究的結果作為實驗室支架製造的一塊基石，期望能幫助實驗室乃至台灣在生醫產業上能更進一步。

Stents are miniature medical devices that can be inserted into arteries and expanded during angioplasty tomaintain patency and re-establish flow through the vessel. They have been the primary treatment for cardiovascular diseases and the alternative treatment for various peripheral arterial occlusive lesions. Laser cutting on Hypotube is the primary manufacturing process. The following step is the electro-polishing to improve the surface quality. To find the proper lacer-cutting parameter for three kinds of material: stainless steel, CoCr and NiTi, some of the important laser-cutting parameters were tested and the lacer-cut stents were electro-polished to test two of the electro-polishing parameters in this thesis. Besides, the unelectro-polished stents were also compared with the electro-polished stents in this thesis.The focus point of the laser, the proper laser power to these three materials and the influence to the cutting quality of the pressure of the assist gas were tested. These three kinds of material were also electro-polished with different time and different electric current to do research on these two parameters.By the measurement of the kerf width, the focus point was found. It’s located under the nozzle around 3.6 mm, and the depth of focus is about 0.16 mm. It was also found that the laser power has small influence on the kerf width, and if the pressure of the assist gas isn’t big enough, some dross will be left over or some material even cannot be removed. For the stainless steel, the pressure has to be higher than 12 bar to make the cutting quality good enough. The experiments show that with the increase of the electro-polishing time, the strut width decreases linearly, and that increasing the electric current accelerates the polishing speed. It is observed that the stent is electro-polished evenly, which means the polishing speed won’t bebadly different between different parts.The proper laser-cutting parameters for three kinds of material to manufacture stent with complete shape were found. It’s also confirmed that the electro-polishing solution and the process used is effective.The achievement done in this thesis provides the basis of stent manufacturing and is expected to improve the biomedicalindustry of Taiwan.