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Femtosecond pulses combat counterfeiting

09 Apr 2008

Product-related counterfeiting is a global problem that can have major social and economic consequences. Eric Mottay of Amplitude Systemes reviews current anti-counterfeiting technologies and the market opportunity for an ultrafast laser solution.

Product trademark recognition, traceability and a robust anti-counterfeiting solution are an essential combination in modern manufacturing methodologies. While industrial laser marking has been driven by the needs of the automotive, electronics, medical and packaging markets, one emerging opportunity lies in anti-counterfeiting technology.

Any market that uses transparent materials or glass containers (such as the beverage, luxury, chemical and pharmaceutical industries) faces specific challenges when it comes to packaging. For example, the pharmaceutical industry uses millions of glass bottles but has to ensure that there are no micro-cracks in the glass in order to maintain the integrity of the vaccine or medicine.

The pharmaceutical industry is constantly vigilant when it comes to quality control, legislation and tracking of products. With the potential profits from counterfeit pharmaceuticals being massive, the industry is also particularly vulnerable to product-related crime. Indeed, it is estimated that 10% of global pharmaceutical industry sales are counterfeit products, and this could be as high as 80% in parts of Asia and Latin America.

The World Health Organisation estimates that 7% of the world's medicines are counterfeit. These fakes lead to many cases of unnecessary illness and death each year as well as losses to the pharmaceutical industry of more than $16 bn, with a good part of this figure going into the hands of organized crime syndicates and terrorist organizations. Not only is there a loss of revenue, but the credibility of the drug company and its brand is put at risk. The answer is an anti-counterfeiting solution that contains a high quantity of information and covers a small and discrete area.

The beverage market, which also uses millions of glass containers, is subject to precise legislation. Every glass bottle must carry important information such as production and use-by dates, a barcode and a serial number. Not only must this information be clearly readable by the consumer but the product's aesthetics must also be considered. The quality of the glass, the production environment and constraints such as transportation and thermal shock all constitute significant challenges that any marking technology must overcome.

The European luxury industry is a major player on the global market. Companies using glass bottles to hold liquids such as perfumes are continuously searching for an aesthetic solution that both improves the promotion of their trademark but at the same time differentiates their products from their competitors and counterfeits. In this case, the complexity of the anti-counterfeiting code coupled with an embedded signature will aid the struggle against fraudulent activities.

Anti-counterfeiting technologies
Innovative anti-counterfeiting solutions are urgently required by the market. The ideal anti-counterfeiting solution should possess a number of key characteristics. Firstly, it must be as close to the primary package as possible – the perfume bottle rather than the cardboard box that it comes in, or the actual pharmaceutical vial rather than a palette. Secondly, the solution must not alter the product or container and be both tamper- and erasure-proof. Finally, and crucially, the solution must be easy to read.

Possible technological solutions for transparent materials include inkjet printing, radio-frequency identification (RFID) and surface or subsurface engraving. The table summarizes the pros and cons of each of these techniques.

Inkjet printing is an attractive technique as inks that cure at high temperatures and form a strong bond to the glass have been developed. Inkjet printers would also be able to print both alphanumeric characters and a data matrix (an array of tiny squares in a pre-determined pattern). To its disadvantage, this approach consumes ink and introduces additional production steps.

RFID is ideal for tracing products but cannot be used as an anti-counterfeiting technology as the information can be cloned, altered or erased. Nevertheless, RFID can be considered as a complementary technology for remote checking of a batch.

Surface engraving using a laser allows alphanumeric characters and data matrices to be etched onto the outside surface of the primary container using nanosecond laser pulses. The drawback here is that these pulses can create cracks and fissures that propagate with time and seriously change the physical structure and strength of the primary container. The code can also be erased by polishing the surface of the container.

Internal engraving
Internal engraving involves focusing a laser pulse into the primary package, either an organic (polymer) or inorganic (glass, fused silica or quartz) material. There are two crucial factors that must be considered. Firstly, the pulsed laser beam should not be absorbed by the material, which rules out ultraviolet or visible lasers. Secondly, the laser intensity must remain below the ablation threshold of the material, which dictates the numerical aperture of the system that focuses the pulses into the material (figure 1).

Nd:YAG lasers emitting nanosecond pulses can create micro-cracks some 50–100 µm in diameter inside a transparent material (see figure 2). This is due to localized thermal effects inside the material that lead to a rise in temperature, increased mechanical stress and, ultimately, fractures in the glass. Such thermal effects are caused by the relatively long pulse duration of YAG lasers (typically 10–100 ns) allowing heat transfer from the laser pulse to the material.

The first generation of lasers used for internal engraving of transparent materials had several limitations. For example, it was not possible to engrave very thin materials as the pulse duration was long enough to produce thermal effects and cracks, which reduced the integrity of the materials.

Micro-cracks are totally forbidden by the chemical and pharmaceutical industry. Other glass containers (engraved bottles of perfumes or wines for instance) must withstand tough transportation constraints (temperature variations, vibration and shocks) and any micro-crack will lead to catastrophic crack growth.

The ultrafast alternative
Ultrafast lasers emitting femtosecond pulses work on a completely different interaction regime compared with nanosecond sources. In the case of ultrafast, the instantaneous light intensity becomes extremely high and allows ablation of virtually any material. In addition, there is no heat dissipation during the interaction process, which essentially becomes athermal, meaning that there is no possibility for micro-cracks or fractures to develop. Other advantages are that the process does not require any additive or post-treatment and that the marking is permanent and can be made virtually invisible. Reliable reading can be achieved under the proper lighting conditions.

The first generation of commercial ultrafast lasers was introduced in the early 1990s. Based on titanium-doped sapphire, these femtosecond lasers were well suited to the research environment but inherent limitations prevented them from being used in industrial applications.

A second generation of ultrafast lasers was developed in the mid-1990s and has been experiencing rapid growth. Ytterbium lasers can be directly diode-pumped, exhibit excellent optical performances and are fully compatible with high reliability, telecom-class laser diodes. Today, with advances in crystals as well as fibre laser technology, ultrafast lasers have both a small footprint and industrial reliability.

Industrial marking system
Under the 6th Framework Research Program of the European Union, an industrial consortium that brought together experts in lasers (including Amplitude Systemes), process development, production-line integration and anti-counterfeiting technologies developed a laser marking system. The project was called Naginels: non-aggressive glass internal engraving system.

The resulting system uses an ultrafast laser for the marking process, an advanced optical reading system and a high-speed sample handling process. In 2007, a company called TrackInside was formed to exploit the commercial potential of the technology in industrial environments.

The TrackInside system has a very high accuracy and its flexible engraving process can create a 60 × 60 µm data matrix as well as logos and text. Although the code can be made invisible to the naked eye, it can be read with a dedicated reading system. A typical marking speed for a 250 × 250 µm, 16 × 16 datamatrix is quoted to be 140 ms while the quality of the marking is consistent with stringent international regulations (grade A–AIM).

• This article originally appeared in the April 2008 issue of Optics & Laser Europe magazine.

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