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Next generation stent manufacturing from Laser Resources

Supplier: LRM Technologies
14 December, 2011

Predicting the future of coronary artery disease treatment is not for the faint of heart.

With dozens of vascular stent designs, materials, anti-proliferative drugs and elution techniques, there is no shortage of potential solutions.

What’s more, different combinations of solutions face a gauntlet of clinical trials and pre-market approvals. That notwithstanding, the fact remains that in 2010, approximately 700,000 U.S. patients had one or more coronary stents implanted, according to the American Heart Association. The majority of those were metal structures (cobalt-chromium, Nitinol, stainless steel) with reservoirs or coatings of an anti-proliferative drug, a compound that inhibits the restenosis process (narrowing of a vessel).

However, the January CE-approval of Abbott’s bioabsorbable vascular stent, ABSORB, and its positive one-year safety and efficacy results in the U.S. may be indications that polymers will soon have a much larger role in the medical device sector than they already do.

While metal stents are extremely efficacious and have been the standard of care for coronary artery disease, stents made of polymeric, bioabsorbable materials promise significant patient benefits. Most importantly, they dissolve away after providing their life-saving vessel support role (typically within 12 months).

With no stent in place, the vessel can resume its natural vasomotion (constriction and dilation), there is no danger of late stent thrombosis (clotting), and there is, generally, no need for long term anti-platelet therapy. What’s more, polymeric stents, even when in situ, do not interfere with the ability to image the chest with CT or MRI technologies, nor the ability of surgeons to go back in to vessels and do further surgical interventions, if necessary.

There is only one catch, but it’s a big one. It’s exceedingly difficult to machine these new materials with traditional tools. Polyglycolic acid (PGA); polylactic, co-glycolic acid (PLGA); polylactic acid (PLA); and polycaprolactone (PCL) all have low melting and glass transition temperatures. Mechanical processing tears them up, and long pulse lasers melt or otherwise compromise the integrity of the materials.

Enter Raydiance’s ultra fast laser technology coupled with ROFIN’s precision workstation engineering. The integration of these two technologies in the StarCut Tube Femto has become an enabling solution for the manufacturing of these next generation stents.

Given the intricate and precise designs of these polymeric devices—strut widths are often 150 µm wide and 150 µm thick—not only is the athermal ablation of the laser key, but so, too, is precise synchronisation of the motion control with the laser pulse delivery.

This is achieved through seamless integration of the laser operating system software with the StarCut Tube workstation. Once a machining design is uploaded to the workstation, the operator chooses the appropriate laser parameters (pulse energy, repetition rate, process gas)—essentially a recipe for a given material type, thickness, and part cycle time—and the workstation takes it from there.

It is a fully automated process. Typically, as-machined bioabsorbable stents are taken from the workstation, wiped with a lint-free cloth and blown with dry nitrogen. No significant post processing steps are necessary.

The StarCut Tube Femto produces high quality, HAZ-free ablation of the traditionally difficult to machine PLLA. For demonstration purposes, a generic stent pattern was machined into this 3.175 mm outer diameter tube. The wall thickness is approximately 214 microns.

Source: Laser Resources Management