Electroforming as a New Method for Fabricating Degradable Pure Iron Stent

Abstract

The first example of a documented electroforming process dates back to 1837 when a layer of electrodeposited copper was found on the surface of a printing plate. Since then, it became a basic manufacturing process to produce delicate metallic components such as nickel thin foils for solar panels, perforated screenprinting cylinders used for fabric and carpet printings, digital recording devices, etc. Recently, electroforming is used for the fabrication of iron-based materials designed for cardiovascular stents. Electroformed iron shows a higher corrosion rate in simulated biological environment; this behaviour is supposed to be influenced by its microstructure which is finer than that of iron produced with traditional techniques. A high corrosion rate can be beneficial for cardiovascular stent applications: a complete stent dissolution in 12-18 months can effectively prevent both late thrombosis and further treatment of paediatric patients, usually requiring a continuous vessel remodelling. Faster corrosion rate of iron-based material is advantageous for cardiovascular stent application in order to avoid late stent thrombosis and arterial growth mismatch in young patients leading to a secondary revascularization procedure. Electroformed iron has mechanical properties comparable to those of stainless steel (stent reference metal) with the advantage of the total dissolution of the material after the accomplishment of its function: for this reason, this metal can be considered as a valid alternative to magnesium-based materials. Nevertheless, electroforming is influenced by parameters such as electrolyte bath composition, current density, pH, temperature, additives, cathode, etc. that have a significant effect on the structure of the produced materials.

Reproduction of Biomimetic Structural Colors via µm‐Scale Ni Textures

“…[3] Although these semiconductor processes produce high-quality nanostructures, they acquire high cost and have limitations in scaling up the size. Meanwhile, self-assembly methods [25][26][27][28] utilizing various building blocks such as block copolymers and colloids have been adopted to reproduce periodic biomimetic structures. However, there exist the issues associated with producing color materials with defect-free on a large scale.…”

“…By adjusting the thicknesses of the Bragg stack and the shape of the microscale texture, it is possible to selectively reflect a desired visible wavelength to reproduce structural colors. Especially, the Ni or Ni-Fe substrates fabricated by the electroforming method [28] can be used to produce the metal texture on a large scale in a mass production manner. This electroforming process can manufacture metallic products in fine A µm-scale Ni texture coated with a dielectric multilayer Bragg stack is developed to cost-effectively reproduce a variety of biomimetic structural colors on a large scale.…”