NANOTECHNOLOGY FOR BANKNOTE SECURITY

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V15 2012 INDEX E-SYLUM ARCHIVE

The E-Sylum: Volume 15, Number 18, April 29, 2012, Article 22

An article in a nanotechnology journal describes an experimental process for adding a cheap power source to banknotes, enabling active radio-frequency identification (RFID) capabilities for anti-counterfeiting and tracking purposes. It's far from reality, but stay tuned. -Editor

"Most passive RFID tags don't have an integrated power source and they receive their power from a radio signal," Husam Alshareef, an associate professor in material science and engineering at King Abdullah University of Science & Technology in Saudi Arabia, explains to Nanowerk. "This means they cannot always perform a memory refresh operation. For applications in banknotes this means the memory used in RFIDs should be non-volatile and rewritable in order to effectively complement logic and sensing elements to provide the desired circuit functionality. Further it should be cheap, flexible, robust and have good retention properties. And fabricating such memory devices on banknotes has been the biggest hurdle so far."

In recent work, Alshareef and his group have now fabricated the first-ever all-polymer, non-volatile, ferroelectric memory on banknotes.

"A major challenge with using banknotes is their rough fibrous surface, which necessitates adding a planarization layer to render the surface amenable to electrode and active layer deposition," says Alshareef. "We overcame this problem by applying a planarizing layer of polydimethylsiloxane (PDMS). In addition to acting as the planarizing layer PDMS provides other important roles such as providing adhesion and strain isolation for the devices above. A key feature of PDMS layer is that it penetrates deep into the fibers of substrates such as banknotes, thus providing strong adhesion without chemical bonding."

Alshareef notes that the performance of their banknote tags is comparable to previous records of pentacene-based ferroelectric transistors on other substrates such as silicon and plastic.

The relevance for the banknote security industry is that these results suggest that the fabrication of high performance non-volatile polymer memories on banknotes is possible – albeit not practical yet.

Alshareef cautions that, in order to make organic electronics on banknotes commercially viable, much work still needs to be done in optimizing printing techniques, improving mechanical integrity, and devising appropriate encapsulation layers.

So will grading services of the future tap into the banknote's memory to learn how many times the note actually changed hands? "This baby was spent by a little old lady in Pasadena who put it in the church collection plate at 10:37 Sunday, June 14, 2023.... And the pentacene-based ferroelectric transistors grade MS-69..." -Editor