Current Trends in Nitinol Stent Manufacturing & Fabrication Processes
Intravascular stents can be manufactured using a variety of different methods, which can be broken down into bottom up and top down approaches. Bottom up methods involve building the stent material and the shape simultaneously, and includes techniques like 3D printing. In a top-down method, the starting point of the fabrication is a large piece of the desired material, and the desired shape is formed by subtractive techniques like etching or laser machining. The selection of the specific fabrication technique is based on a combination of the inherent properties of the stent material, and the shapes required.
Due to the difficulty of synthesizing nitinol, including the requirement for very high temperature and extreme sensitivity of its properties to composition and synthesis temperature, top-down methods are used to fabricate stents and other medical devices from nitinol. Currently, the two most common fabrication methods are laser machining and photochemical etching, which will be described in detail below. Today, nitinol devices are generally fabricated from a thin-walled nitinol tube or wire, or in some cases a thin nitinol sheet.
Note that nitinol is a relatively hard material, with a Rockwell hardness of roughly 60, which is similar to steel. Specially designed cutters with sharp cutting edges made of hard materials are recommended for high quality, precise cuts. These cutters should be cleaned and inspected regularly, and should be replaced if they become damaged or dull.
A second, though less common method for fabricating nitinol medical devices is photochemical etching. In this method, a piece of nitinol tube, wire, or other shape is selectively masked, then exposed to a chemical etchant.
The main advantages of this technique are that it avoids the formation of burrs and redeposited material that can be an issue with laser machining, and does not involve the exposure of any area of the stent to high temperature. However, the processing speed is generally slower than laser machining, and is best suited for making 2-d shapes, unless the desired 3-d shape can be made by folding or rolling.
One trend in this area involve the use of alternate and less hazardous chemicals in the etching procedure. A second is the incorporation of microfabrication techniques, including photolithography and thin film deposition, to fabricate more intricate, precise, and three dimensional shapes .
Fabrication of intravascular nitinol stents is a highly demanding and precise process. It is typically done using laser machining, using fast pulses to reduce the heat load on the part, or less commonly by selective chemical etching. Recent trends in this area include the use of more advanced laser pulsing technology, laser processing to control material properties while cutting, and the incorporation of microfabrication techniques. Handling nitinol raw materials and finished parts often involves cutting, which requires use of hardened cutters made for this type of material.
For over 40 years, Lab Pro has been committed to delivering the highest quality cutters and tweezers to tech laboratories worldwide. Come visit the biggest Lab Supply showroom in California, or contact us online or at 888-452-2776.