Lasers & photonics
optical in nature, traditional manufacturing lasers can struggle, particularly when it comes to damaging the device. Yet the situation is far from hopeless. For amid the proliferation of nanosecond devices, so named for the laser pulses they emit, a newer range of femtosecond lasers are appearing too. Boasting much faster pulses than their nanosecond cousins, they can focus energy to remarkably precise points, ensuring hollows are dug or seams welded without harming surrounding material. Not that manufacturers can necessarily expect to seamlessly convert to femtosecond solutions. As so often, reliability is one difficulty. Price, for its part, is another. And while both these stumbling blocks are gradually being softened thanks to widening adoption, and the market forces that implies, researchers are tackling problems around low manufacturing throughput via the clever use of technology. Not that every manufacturing challenge should necessarily be solved by femtosecond lasers. For while their value is indisputable, particularly for manufacturing sophisticated devices like cardiovascular stents, other products may actually be produced better using older lasers – especially if cost is an issue.
Cutting crews It’s hard to overstate the importance of lasers across medical device manufacturing. Consider something as straightforward as welding. Excellent at combining metallic materials, they’re crucial for the manufacture of pacemakers and stents. That’s true in other areas too. As Professor Robert Thomson, a photonics expert at Heriot-Watt University highlights, lasers can equally be employed for drilling holes in needles and catheters, or else marking (engraving) implants and surgical tools. That’s echoed, adds Duncan Hand, another Heriot-Watt professor and laser expert, by 3D printing, where lasers can be used to print complex electrical structures onto living organisms. Quite beyond the headline industry growth, meanwhile, this enthusiasm is apparent if you examine specific firms. Stryker, for instance, has been investing in laser manufacturing capabilities for years, while Medtronic has recently focused on using lasers to enhance the surface textures of devices. Listen to the experts, and this popularity can fundamentally be understood in terms of how lasers works. Targeting pulses, and the energy they emit, to very specific areas, they can cut holes or dig groves – all without damaging nearby material. Beyond the benefits for intricate and fragile medical components, that’s equally helpful for manufacturers wishing to create lattice structures from materials. Among other things, these lattices
Medical Device Developments /
www.nsmedicaldevices.com
can mimic bone (stimulating ingrowth) and change the mechanical behaviour of existing materials (reducing the need for complex polymers). As Thomson summarises: “In comparison to conventional manufacturing approaches, such as mechanical drilling, lasers offer the potential for micron-level precision, they are more flexible in terms of the range of materials to which then can be applied, they can provide a cleaner, more repeatable, and potentially more environmentally friendly manufacturing process, and they do not exhibit tool wear.”
By the 1970s, the technology was used regularly in specialised sectors.
“Lasers offer the potential for micron-level precision...and they do not exhibit tool wear.”
Robert Thomson
Despite these general advantages, however, the properties of some lasers can also cause frustration. As Dr Koji Sugioka of the Riken Center for Advanced Photonics explains, that’s basically down to speed. “The important factor for materials processing using lasers,” he says, “is the electron-phonon coupling time of materials – which is the time during which the laser energy absorbed by electrons is transferred.” The problem, continues Sugioka, is when the pulse width of a particular laser is longer than the electron-phonon coupling time. That can spread the laser heat to other areas, along the way causing severe damage. Of course, this can be disastrous, both technically and financially, especially now that miniaturisation is the order of the day right across medical device manufacturing.
Laser focus
Given the limitations of longer pulse lasers – notably the nanosecond variety – it makes sense that researchers should have focused many of their efforts on short-pulse alternatives.
$26bn
The expected size of the global laser processing market by 2027.
Research and Markets 77
SasinTipchai/
Shutterstock.com
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