Laser processing of medical devices

Materials World magazine
,
1 Dec 2007
Lasers

As global healthcare needs increase and evolve, novel and more intricate laser tooling applications will grow in demand. That was the conclusion reached by attendees at a conference on Opportunities for Laser-based Manufacturing in the Medical Sector, held in West Bromwich, UK, on 7 November 2007.

Dr Gerard O’Connor of the National Centre for Laser Applications in Galway, Ireland, discussed the country’s growing use of lasers for the production of medical devices.

‘Our first significant application of lasers was Excimen [UV] laser profiling to remove excess material from catheter tips,’ said O’Connor. This spawned other applications, including laser marking of pacemakers, and laser welding and cutting of stents.

Lasers can create products with smooth, even edges, causing less trauma for patients. And with their acceptance by the US Food and Drug Administration, the path is open for their continued use in healthcare manufacturing.

However, ‘Governments are requiring more documentation on medical process parameters’, noted Alexander Knitsch of Trumpf GmbH, producers of medical technology based in Schramberg, Germany. This puts demands on manufacturers to create lasers that are stable, have long lifecycles, and are biocompatible with the base material – usually stainless steel, titanium or nitinol.

Trumpf has recently released short and ultra short pulse lasers for ablation which the company believes meet these requirements. The devices have also shown promise for stent cutting without causing thermal damage, a common problem with laser processing.

One of the biggest benefits of lasers is their ability to operate down to the microscale – a necessary feature as medical nanotechnologies evolve. ‘A lot of these products couldn’t be made economically by any other means,’ said Jonathan Magee of laser manufacturers Rofin-Baasel UK Ltd, based in Daventry, UK.

The cutting, smoothing, sealing and stamping of stents for arteries was a major focus of the day’s event. Using a fibre laser, Rofin-Baasel has welded together stainless steel wires that are 25 microns in diameter. This technology can create nano-stents in less than 60 seconds – one of the fastest times in the world, said Magee.

The low heat input of laser welding and cutting also makes it ideal for use on dissimilar materials, said Neil Ball, President of Directed Light Inc in San Jose, USA. Ball’s company has used neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers to seal titanium nanotubes with a radioactive centre for cancer treatment. ‘No other process could seal in something that small so precisely,’ explained Ball.

When it comes to micro applications, none of the lasers are as fine and detailed as femtosecond and picosecond lasers, which can operate below 10 microns, he said. But these devices ‘still need improvements in their control and speed’ when it comes to pulse durations, spacing and energy levels. Ball, like others at the event, has decided to hold off investing in this technology until those problems have been addressed.

 

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