Safety is a top priority in medical technology. Not only does this apply to finished medical devices, it also pertains to individual components: Counterfeit parts jeopardize the proper functioning of a device and consequently the patient. In the future, suppliers could use color laser markings to protect components from forgery.
In this interview with COMPAMED-tradefair.com, Carl Gehrmann talks about the marking of components with ultrashort pulse lasers and explains why these markings are as unique as a fingerprint.
Mr. Gehrmann, photonicfab offers laser markings to protect products against piracy. How are these markings made?
Carl Gehrmann: Lasers have been recognized as tools to mark products for some time. Nowadays, nanosecond pulsed laser systems are used to create barcodes and serial numbers on devices. In recent years, ultrashort pulse lasers or USP lasers have likewise become increasingly popular. These are lasers that create pulses in the picosecond or femtosecond range. They create better black marking than nanosecond lasers. These markings also feature a higher contrast and are more resistant to cleaning processes in autoclaves or ultrasonic cleaners.
At photonicfab, we have developed a marking technology that produces so-called laser-induced nanostructures that diffract the light and thus create the kind of holographic effect we know from ID documents or banknotes. This type of marking is an obvious security feature for every product user.
How exactly are these nanostructures created?
Gehrmann: These are stochastic structures that automatically form in the laser focus. We work with a laser wavelength between 500 nanometers and 1 micrometer. In this dimension, this creates slits in every laser spot in the material that diffract the light and produce the holographic effect. We can use this effect for any markings such as DataMatrix codes, logos or IDs for example. This works especially well on metals, though this type of marking can also be applied on polymers.
The markings on this piece of metal have been made using an ultrashort pulse laser. In appears in different colors, depending on the angle of the light.
What makes these markings so unique?
Gehrmann: They have an approximate slit spacing that is related to the laser wavelength. The resulting pattern is as unique as a fingerprint. This also depends on the grain size of the raw material and whether there are any imperfections for example. This is why you cannot counterfeit an individual marking even if you use the same laser system. Having said that, the challenge is to read the marking. There is still some room for improvement in this area.
Gehrmann: From the outside, the onlooker notices the holographic effect as an obvious security feature. Yet if a manufacturer wants to be 100 percent certain, they have to read the microstructures – first, right after the marking to record and save it and once again for recourse purposes to verify it. In actuality, the marking would have to be read for each individual component. And although this would be quite an elaborate process, it could be justified when it comes to safety-related components. Meanwhile, in the case of polymers, you could mark an injection mold to be able to, later on, identify the tools that were used to cast each component.
The readout is possible via a high-resolution optical microscope or laser scanning microscope. Another option is a scanning electron microscope. However, this process would be elaborate and expensive.
What pros and cons do you see in the ultrashort pulse laser marking process compared to other marking techniques?
Gehrmann: One drawback is the price. Even though laser source costs continue to fall, the marking technique with USP laser is still about ten times more expensive than nanosecond laser marking.
The higher resolution of USP lasers is clearly a major advantage because it allows us to produce more refined structures. What’s more, the marking features a higher contrast and durability. It also facilitates diffractive structures, meaning holographic effects on surfaces, but that is not an essential factor.
The interview was conducted by Timo Roth and translated from German by Elena O'Meara. COMPAMED-tradefair.com