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Oxonica has developed the Nanobarcodes TM particle system which consists of striped submicron
scale metallic rods. The Nanobarcodes TM make use of the different reflectivity of
gold, silver and platinum. The codes are read using an optical microscope through
proprietary software. One thousand of such rods can generate trillions of unique codes.
For example, 5 stripes with 2 different metals can generate 20 unique codes and 3
metals can generate 135 unique codes. An illustration and microscopy image of
Nanobarcodes TM is given in Figure 4.3. These nanobarcodes can be used for covert
security in inks, adhesives, laminates, paper, packaging, and films. The proprietary
technology can also be used for applications in textiles, thread, and glass (Wakefield,
2007).
Figure 4.3 a) Schematic of the Nanobarcodes TM , b) Microscopy Image showing dark and light
strips of silver and gold based on the difference of reflectivity at the observation wavelength. 17
SERS tags, originally developed by Nanoplex technologies, use the principle of Raman
scattering. Since all substances have unique spectra of scattered light, it can be
effectively used as an identification tool. A SERS tag (as shown in figure 4.4) would
typically consist of a core metal nanoparticle, SERS reporter and a coating of a material
such as silica. Nanoparticles of gold and silver are primarily used for SERS tags. The
applications of SERS tags include bank notes, paper, packing, clothing and pills. The
main disadvantage in Raman scattering is the weak signal, however this can be enhanced
by using surface enhancement. The advantage of SERS tags is that they are difficult to
counterfeit due to the infinite number of unique codes. They are covert, non-toxic, and
multifunctional. The tags can be read without contact at a distance of up to 1000 metres,
in one second. These tags are also used in diagnostic applications (Wakefield, 2007).
Figure 4.4 Image of a SERS tags used in diagnostic applications
17 Dougherty, G.M.: Microfluidic systems for solution array based bioassays http://www-
eng.llnl.gov/pdfs/mic_nano-1.pdf
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