Chapter 4 STENT DESIGNS Stents are small meshed spring like tubular structures used in angiolplasty to treat the narrow or weak coronary arteries that carry blood. The implantation of stent prevents the arteries from blowing out for a longer duration after surgery. One of the causes for blockage of arteries is the plaque deposition in the inner parts that eventually block the blood flow and may also lead to heart attacks. Stents are embedded in the arteries by the process called as PCI. In PCI stents circum surfaces a balloon attached to a flexible tube which is inserted in the body through thighs. After reaching the desired location, balloon is inflated in
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Due to the large set up and heavy investments it can be used only in large scale production. Initially it was used for production of stainless steel stents. Later the process was extended to other materials like nitinol followed by joining processes and forming. The reduction in HAZ and stress free machining makes this a favourable process for stent manufacture. Due to low aspect ratio this method cannot be extended to stents of all designs.
Thin film technology Stent manufacturing requires precision and tight tolerances which can be successfully achieved by this method. If the stents surface after manufacture is contaminated then it increases the clot forming tendency of blood. Thin film technology gives unadulterated surface finish which makes it a favourable method. .In radically high vacuum atmosphere sputters are deposited on planar or rotating substrate. [1]
Electroforming
Though Electroforming process also has the ability to handle precise and intricate stent designs it is not commercially used as it is not applicable to stainless steel and commonly used materials. Photo resists are made of a particular stent design and electroplating is done on a mandrel with a photo resist. The resist is then exposed to UV rays to form the stent image. Electroformed stent is produced by dissolving the resist and …show more content…
The different geometric parameters influence performance of stents in terms of deliverability, scaffolding and recoil. This may cause impact in stent life and restenosis. Stents can be made from sheet, round or flat wire or tubing. The vast majority of coronary stents are produced by laser cutting from tubing as it is one of the easiest manufacturing technique and slotted stent type designs are known for excellent radial strength. The 3-D geometries of the stents created in the available modeling software of SolidWorks 2012 are described below.
Sheet based Design
Stent Design A The sheet based model was created in planar state , visualizing the actual stent cut open longitudinally and made planar.The nanocomposite sheet of 0.14mm thickness and 24mm length is bent and joined to form a metallic tubular structure of diameter 4mm. The uniform thickness of the stent is 0.14mm over the entire length of 24mm.Peak to Peak pattern is used to design the stent as shown in the figures above. The solid model generated is of the stent in a planar state of geometry if it was cut open longitudinally and flattened
Due to the large set up and heavy investments it can be used only in large scale production. Initially it was used for production of stainless steel stents. Later the process was extended to other materials like nitinol followed by joining processes and forming. The reduction in HAZ and stress free machining makes this a favourable process for stent manufacture. Due to low aspect ratio this method cannot be extended to stents of all designs.
Thin film technology Stent manufacturing requires precision and tight tolerances which can be successfully achieved by this method. If the stents surface after manufacture is contaminated then it increases the clot forming tendency of blood. Thin film technology gives unadulterated surface finish which makes it a favourable method. .In radically high vacuum atmosphere sputters are deposited on planar or rotating substrate. [1]
Electroforming
Though Electroforming process also has the ability to handle precise and intricate stent designs it is not commercially used as it is not applicable to stainless steel and commonly used materials. Photo resists are made of a particular stent design and electroplating is done on a mandrel with a photo resist. The resist is then exposed to UV rays to form the stent image. Electroformed stent is produced by dissolving the resist and …show more content…
The different geometric parameters influence performance of stents in terms of deliverability, scaffolding and recoil. This may cause impact in stent life and restenosis. Stents can be made from sheet, round or flat wire or tubing. The vast majority of coronary stents are produced by laser cutting from tubing as it is one of the easiest manufacturing technique and slotted stent type designs are known for excellent radial strength. The 3-D geometries of the stents created in the available modeling software of SolidWorks 2012 are described below.
Sheet based Design
Stent Design A The sheet based model was created in planar state , visualizing the actual stent cut open longitudinally and made planar.The nanocomposite sheet of 0.14mm thickness and 24mm length is bent and joined to form a metallic tubular structure of diameter 4mm. The uniform thickness of the stent is 0.14mm over the entire length of 24mm.Peak to Peak pattern is used to design the stent as shown in the figures above. The solid model generated is of the stent in a planar state of geometry if it was cut open longitudinally and flattened