APPLICATION FOCUS: MEDICAL DEVICE MANUFACTURING MEDICAL MARKING


New regulations dictate that certain medical devices must be marked with a unique device identification code. Here we explore how different laser technologies can be used to produce these markings


E (MDR)1


uropean manufacturers and distributors of medical devices are currently adapting their processes to the latest requirements of the new Medical Device Regulation , introduced in 2017 by the European


Union. Te manufacturers are coming to the end of


a subsequent three-year transitional period – ending in May 2020 – that has allowed them to ensure their processes, data and documentation meet the requirements of the new regulation, which aims to ensure better protection of public health and patient safety. One of the demands of the new regulation is


that a comprehensive EU database of medical devices be established, along with a device traceability system based on the use of unique device identification (UDI) marks. Similar demands were already made in America towards last year, when on 24 September, under FDA regulations, it was made mandatory that re-usable, non-implantable, class II medical devices bear a permanent UDI mark. UDI-codes applied directly on medical


devices, such as surgical instruments and implants, make every single item explicitly traceable throughout its product life cycle, from manufacturing to usage on a patient. In addition to this being important for the safety of patients and the enhancement of product quality, it is also of important – with the increasing digitalisation of the health sector – that these codes be of high contrast, in order to be both human and machine-readable. Considering the extensive repeated


processing in medical practice, these requirements place especially high demands on the lasting stability and reliable machine


26 LASER SYSTEMS EUROPE ISSUE 42 • SPRING 2019


Pulsed lasers can be used to produce


high-contrast UDI mark- ings on medical devices that are resistant to corrosion and repeated sterilisation and cleaning cycles


readability of the UDI mark. Over the product lifecycle, the marking must be reliably resistant against corrosion and fading, especially against the hundreds of rigorous cleaning procedures – for example steam sterilisation accompanied by a high alkaline (pH 14) cleaning process2 – that the devices will have to undergo through everyday clinical use. Laser marking is ideal for the


direct marking of medical devices. It is fast, precise – some parts, such as bone screws2


,


require markings as small as 0.2mm – economic, automatable, and is well-suited for volume production.


marks are more permanent and less restrictive to use than nanosecond laser marks


Ultrafast marking According to laser manufacturer Coherent3


, a


problem exists when traditional laser marking applications involving CO2 lasers, solid-state nanosecond (DPSS) lasers, and continuous- wave fibre lasers, are used to create markings on medical devices made from stainless steel. In a photothermal process, these lasers use a


tightly focused beam to deliver intense heat in a highly localised manner, raising the material temperature to induce a change, such as a colour change or an engraving on the surface.


Picosecond laser


A near-infrared output from fibre lasers or DPSS nanosecond lasers, for example, can be used to produce high-contrast black marks. Te black appearance of these marks, however, is primarily due to the creation of an outer layer of oxide, which can compromise the corrosion resistance of the surface. Re-passivation of the medical device – the stainless steels alloys used already have a natural passivation outer surface of chromium oxide – is therefore required following this process, according to Coherent, which typically causes this type of mark to fade. In addition, for multi-use products, oxide marks also fade with repeated autoclaving,


causing the contrast to eventually reduce below a level readable by certain machines. It is therefore recommended by Coherent


that picosecond lasers are used for the marking of stainless steel medical devices. Tis is because the pulse duration they offer is typically shorter than the time for heat to flow out of the laser interaction zone, even in metals, so peripheral thermal effects are vastly reduced, compared to nanosecond lasers. In addition, a much higher portion of the total laser power is used to remove material, rather


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