Ultrafast laser used in medical stent cutting

Medical equipment is a product with high added value, which has strict quality requirements and usually requires the use of challenging industrial manufacturing processes. For these reasons, ultrafast lasers have been widely used in the field of medical equipment manufacturing.　　The famous application is stent manufacturing. A stent is a prosthesis made of metal or polymer. It can be used for dilatation, allowing blood to flow into the occluded artery when the blood vessel or cavity is narrowed or occluded. The laser cutting stent is of excellent quality and versatile, and is now the main manufacturing process for the stent and its auxiliary tools.　　A typical stent is a small tube whose frame is cut with a laser beam, so the performance of the tube is similar to a spring, which can prevent arterial contraction after surgery. Depending on the model and manufacturer, the diameter of the stent ranges from 1.2 mm to 3.5 mm, and the wall thickness ranges from 0.10 mm to 0.25 mm. Three different stents can be considered: 　　● Simple stents made of metal, stainless steel (80%) or Nitinol (that is, a shape-memorable alloy containing nickel and titanium, 20%).　　● The metal bracket is added with some active materials to prevent the passage from becoming narrow again. Take several steps to wash out u0026 rdquo; add active material to the stent to improve the durability of the stent. The elution is performed by a miniature reservoir or coating on the stent. These stents account for the major share (greater than 75%) of actual stent surgery each year.　　● The recent bioabsorbable stents are generally made of PLLA (polylactic acid) polymer. Active substances can also be added to these products. When used, the stent slowly degrades and gradually melts into the blood after the artery has healed. This process can take several months or as much as one or two years. Recently, the bioabsorbable polymer stent has passed CE certification and can be used in Europe. Since the bioabsorbable stent is made of polymer, this material is extremely sensitive to thermal effects. When long-pulse laser is used for machining, it cannot guarantee good enough quality, and the cutting process will generate heat, so it needs to be manufactured by ultra-fast laser processing technology. These brackets can achieve high-quality manufacturing effects.　　 On the other hand, nowadays, long-pulse lasers are used to process metal stents, and the pulse width is usually s or ns.　　The application of laser cutting technology started from the pipeline, which is only a part of the stent manufacturing process. Other processes include trimming, mechanical extension and heat treatment, electro-polishing, disinfection and sterilization, and packaging. Depending on the purpose of the laser, water flow is used in the pipe for wet cutting during laser cutting. The auxiliary gas can also improve the overall cutting quality. Generally, the cutting width is 10 to 20 m, the accuracy is 5 m, and the cutting speed is 5 mm/s.　　Post-processing steps account for most of the total manufacturing cost. Because the quality of ultrafast laser cutting machine cutting metal is better than that of long pulse laser, the cost of the later processing stage is greatly reduced.　　Total manufacturing cost includes amortized laser investment, laser working cost and post-processing cost. The investment cost of ultrafast lasers is generally higher than other technologies. However, their work costs are low, and they can also significantly reduce post-processing costs. In addition, due to the continuous improvement of laser power and repetition rate, this will greatly increase processing output.　　 All these factors have promoted the massive growth of the application of ultrafast lasers in stent manufacturing, and this trend will continue in the next few years.