膽管支架(Biliary Stent)為一種中空管狀結構的醫療器材，主要目的為支撐膽管壁，使膽汁可以順利通過阻塞的膽管，可降解支架使用的材料為聚乳酸PLA(Polylactic Acid)，PLA支架的優點在於可以被身體吸收，故不須再進行二次手術將支架取出，並具有足夠的機械強度及生物相容性。
現今的支架，大多是以雷射加工製造而成，也因為雷射的特性，使得支架側壁呈現銳角結構，而雷射加工後的支架需仰賴後處理製程達到去除銳角結構。透過CNC(Computer Numerical Control)五軸加工對可降解材料加工的文獻，至今為止仍較少人進行這方面的探討，包括加工參數、工法、胚料製備等等，因此本研究以微銑削的方式進行可降解支架的探討，利用微小徑球型刀進行支架加工，且同時將支架邊緣圓角化，改善支架壁邊銳利邊角的問題，透過實驗建立出CNC五軸機對PLA加工時的參數標準，以及最少毛邊生成量的結果。
本研究以五軸加工機微銑削生物可降解支架，主要先利用積層製造的方式製作出胚料。為提升積層製造胚料精度，在加工前會進行外部銑削，確保外徑尺寸。因PLA材料比起金屬強度較低，加工時易產生彎曲(bending)現象，故本實驗為了避免該現象，透過深度的分層加工，降低加工時對胚料產生的壓力，以達到減少彎曲量與改善實際切深。經實驗證實以微銑削方式確實能成功加工生物可降解支架，並同時將支架銳角去除，且結構完整不被銑削時的路徑破壞。本研究成功製作出直徑10mm、厚度0.6 mm、圓角0.15R之生物可降解支架。

Biliary stent is a medical device with a hollow tubular structure. The main purpose is to support gallbladder duct wall in order that bile can pass through the blocked bile duct smoothly. The common material used for the degradable stents is polylactic acid (PLA). The PLA stent will be completely absorbed by the body; therefore, it is unnecessary to operate the secondary surgery to remove the stent. Also, there will be less problem of re-clogging. The stent can be implanted in human body with sufficient mechanical strength and biocompatibility.
Nowadays, most of the bile duct stents are manufactured by laser processing, which makes the acute angle structure present on the side wall of the stent. It may cause unpredictable injury to the vessels due to a sharp angle of the stent in medical treatment. In this study, the manufacture of degradable stents was performed by means of micro-milling. Miniature ball-shaped cutters are used to process PLA stents and to improve the problem of sharp edges.
This research was conducted the biodegradable stents that were milled by using a five-axis machine. The main process is to use an additive manufacturing method to produce a base material, in order to improve the precision of the additive manufacturing , external milling is performed before machining to ensure the outer diameter. Because the PLA material is less than the metal strength, it is easy to bend during processing.In order to avoid this phenomenon ,The depth of the layered processing is used to reduce the pressure on the billet during processing to reduce the amount of bending.Improve the actual depth of cut. And it has been verified that the acute angle of the stent struts can be removed by micro-milling. This study successfully produced biodegradable, which is 10mm in diameter, 0.6 mm in thickness, and 0.15R in radius, through experiments.

[1] 林孟頡，「以環形熱壓轉印技術開發生物可降解支架」，碩士論文，國立台灣科技大學，2013。
[2] 台北榮民總醫院，一般外科學術論文專題-胰臟癌，2017，Available at : https://wd.vghtpe.gov.tw/gs/Fpage.action?muid=863&fid=3908。
[3] S. A. Khan; H. C. Thomas; B. R. Davidson; S. D. Taylor-Robinson. "Cholangiocarcinoma" , The Lancet, 2005,vol. 366: 1303-1314.
[4] S. E. Lee; J. Y. Jang ; Y. J. Lee ; D. W. Choi ; W. J. Lee ; B. H. Cho ; S. W. Kim. "Choledochal cyst and associated malignant tumors in adults: a multicenter survey in South Korea " , Archives of Surgery, 2011, vol.146: 1178-1184.
[5] S. Awad; A. M. Zaitoun ; D. N. Lobo. "Blocked metal biliary stent" , Journal of gastroenterology and hepatology, 2011, vol.26: 1694-1694.
[6] J. T. Bueno; H. Gerdes; R. C. Kurtz. " Endoscopic management of occluded biliary Wallstents" , a cancer center experience. Gastrointestinal endoscopy, 2003, vol.58: 879-884.
[7] J. N. Rogart; B. Ara; R. Federico; M. D. Hashem Al-Hashem; D. S. Uzma; M. D. Priya Jamidar; A. Harry. "Analysis of endoscopic management of occluded metal biliary stents at a single tertiary care center" , Gastrointestinal endoscopy, 2008, vol.68: 676-682.
[8] L. C. Ornellas ; G. Stefanidis; R. Chuttani; A. Gelrud; T. B. Kelleher; D. K. Pleskow. "Covered Wallstents for palliation of malignant biliary obstruction: primary stent placement versus reintervention" , Gastrointestinal endoscopy, 2009, vol.70: 676-683.
[9] H. Isayama; Y. Komatsu; T. Tsujino; N. Sasahira; K. Hirano; N. Toda; Y. Nakai; N. Yamamoto; M. Tada; H. Yoshida; Y. Shiratori; T. Kawabe; M. Omata. "A prospective randomised study of “covered” versus “uncovered” diamond stents for the management of distal malignant biliary obstruction" , Gut, 2004, vol.53: 729-734.
[10] 肝病防治學術基金會，膽道支架如何選擇，2018，Available at : https://www.liver.org.tw/newsView.php?cat=3&sid=20。。
[11] 林清安，「適用任意五軸工具機台結構之 NC 加工路徑後處理 之理論研究與實務開發」，個別型計畫，國立台灣科技大學，2013。
[12] G. P. H.Gubbels; G. J. F. T.Van Der Beek; A. L. Hoep; F. L. M. Delbressine; H.Van Halewijn. "Diamond tool wear when cutting amorphous polymers" , CIRP Annals-Manufacturing Technology, 2004, vol.53: 447-450.
[13] K. Q. Xiao; L. C. Zhang. "The role of viscous deformation in the machining of polymers" , International journal of mechanical sciences, 2002, vol.44: 2317-2336.
[14] R. Auras; B. Harte; S. Selke. "An overview of polylactides as packaging materials", Macromolecular bioscience, 2004, vol.4: 835-864.
[15] L. T. Lim, ; R. Auras; M. Rubino. "Processing technologies for poly (lactic acid) " , Progress in polymer science, 2008, vol.33: 820-852.
[16] K. M. Nampoothiri; N. R. Nair; R. P. John. "An overview of the recent developments in polylactide (PLA) research" , Bioresource technology, 2010, vol.101: 8493-8501.
[17] X. Zhang; M. Espiritu; A. Bilyk; L. Kurniawan. "Morphological behaviour of poly (lactic acid) during hydrolytic degradation" , Polymer Degradation and Stability, 2008, vol.93: 1964-1970.
[18] F. Codari; S. Lazzari; M. Soos; G. Storti; M. Morbidelli; D. Moscatelli. "Kinetics of the hydrolytic degradation of poly (lactic acid) " , Polymer degradation and stability, 2012, vol.97: 2460-2466.
[19] F. Iniguez-franco; R. Auras; G. Burgess; D. Holmes; X. Fang; M. Rubino; H. Soto-Valdez. "Concurrent solvent induced crystallization and hydrolytic degradation of PLA by water-ethanol solutions" , Polymer, 2016, vol.99: 315-323.
[20] B. Bax; Müssig, Jörg. "Impact and tensile properties of PLA/Cordenka and PLA/flax composites" , Composites science and technology, 2008, vol.68: 1601-1607.
[21] D. H. Kim; S. G. Kang; J. R. Choi; J. N. Byun;Y. C. Kim; Y. M. Ahn. "Evaluation of the biodurability of polyurethane-covered stent using a flow phantom" , Korean journal of radiology, 2001, vol.2: 75-79.
[22] L. Xu; K. Crawford; C. B. Gorman. "Effects of temperature and pH on the degradation of poly (lactic acid) brushes" , Macromolecules, 2011, vol.44: 4777-4782.
[23] 高慶隆，「5-French鎳鈦膽道支架研發」，碩士論文，國立台灣科技大學，2017。
[24] 陳彥喬，「以五軸加工技術製作生物可降解支架」，國立台灣科技大學， 2016。