Fibre Laser Cutting and Chemical Etching of AZ31 for Manufacturing Biodegradable Stents

Abstract

The use of magnesium-alloy stents shows promise as a less intrusive solution for the treatment of cardiovascular pathologies as a result of the high biocompatibility of the material and its intrinsic dissolution in body fluids. However, in addition to requiring innovative solutions in material choice and design, these stents also require a greater understanding of the manufacturing process to achieve the desired quality with improved productivity. The present study demonstrates the manufacturing steps for the realisation of biodegradable stents in AZ31 magnesium alloy. These steps include laser microcutting with a Q-switched fibre laser for the generation of the stent mesh and subsequent chemical etching for the cleaning of kerf and surface finish. Specifically, for the laser microcutting step, inert and reactive gas cutting conditions were compared. The effect of chemical etching on the reduction in material thickness, as well as on spatter removal, was also evaluated. Prototype stents were produced, and the material composition and surface quality were characterised. The potentialities of combining nanosecond laser microcutting and chemical etching are shown and discussed.

A strain-mediated corrosion model for bioabsorbable metallic stents

“…A macroscale corrosion damage internal state variable model that captured the effects of multiple corrosion processes (general, pitting and intergranular corrosion) was developed by [3] and applied to the AZ31 magnesium alloy, an alloy that has been used in metal biodegradable stents [4]. Models of other corrosion processes have been developed and applied to magnesium alloys such as stress corrosion cracking (SCC) [5] fatigue cracking [6] and crevice corrosion [7].…”

Laser surface structuring of AZ31 Mg alloy for controlled wettability

“…As a matter of fact, for specific cases such as cardiovascular stents, laser surface structuring can be implemented within the same machining setup used for laser cutting of the implant. 27 In this work, the use of a pulsed fiber laser source to change surface structure of AZ31 Mg alloy is studied to control wetting behavior with the aim to improve adhesion. A single-step strategy based on surface remelting was employed based to generate five different surface types.…”

Comparative study of CW, nanosecond- and femtosecond-pulsed laser microcutting of AZ31 magnesium alloy stents

“…In literature, limited amount of work regarding laser microcutting of stents is reported, where CW emission, 15 longpulsed, 14,16,17,21,22 short-pulsed, 23 and ultrashort pulsed 24,25 sources are used on different materials. A comparison regarding the different machining domains appears to be absent to authors' knowledge.…”

“…A comparison regarding the different machining domains appears to be absent to authors' knowledge. On the other hand, in the literature, manufacturing of Mg alloy biodegradable stents has been treated sparingly, 23,26,27 despite the presence of clinical trials of commercial stents on animal models and human patients. [28][29][30] This paper investigates laser microcutting of AZ31 alloy with three distinct laser cutting regimes for biodegradable magnesium stents.…”

“…Moreover, it has been observed in previous studies that the process window of laser microcutting is limited. 23 In a fixed pulse duration condition, indeed the margin of quality improvement is limited due to the geometrical restrictions of cutting a microtube. Therefore, it has been intended to report representative microcutting conditions that allow a comparison in pulse duration parameter space (i.e., continuous, ns, and fs).…”