The E-Sylum:  Volume 10, Number 24, June 17, 2007, Article 23

CHEMISTRY-BASED ANTI-COUNTERFEITING TOOLS

We've discussed a number of new and proposed banknote anti-counterfeiting
features in The E-Sylum.  The June 11 issue of Chemical & Engineering
News notes that chemistry could play a major role in future deterrents
against currency fraud.  The lengthy article was derived from the same
recent National Research Council (NRC) report on counterfeiting, but
focuses on the chemistry involved in some of the anti-counterfeiting
solutions.

"Advanced currency must include 'features that are based on the
molecular properties of the materials themselves,' says Alan H.
Goldstein, who was an Alfred University professor of biomaterials
when he helped produce the report. 'There's not a huge market for
the home materials fabrication facility, the way there is a market
for the home reprographic facility.'

"Small print Dip-pen nanolithography uses an atomic force microscope
tip to write with molecular 'inks.' The technique could be used to
inscribe banknotes with print that has dimensions in the nanometer
range.

"Surprisingly, piling too many security features onto a note can
backfire. Some banknotes, such as the euro, are so loaded with
complex features that they confuse consumers, who can't remember
what to check for, Goldstein says. Japan has opted instead for a
pared-down approach that points consumers to one dominant
anticounterfeiting feature: In the center of each banknote is a
large, empty oval. It virtually begs the user to hold the bill up
to the light to verify that a watermark portrait appears.

"... the committee proposes that any new security feature should
engage in dynamic behavior only when directly stimulated by a user.
For instance, a cashier could squeeze a bill or hook it up to a
battery to induce a response that verifies the bill's authenticity.

"One such response could rely on piezoelectric materials. Voltage
provided by a battery can reversibly change the shape of these
materials, which are typically based on quartz or lead zirconate
titanate. Polymer-based piezoelectric elements are also under
development. If these materials were embedded in a section of a
banknote, their shape change could, for example, raise bumps that
alter the surface texture from smooth to rough and back.

"Alternatively, a consumer could squeeze a banknote containing a
piezoelectric material hooked up to an organic light-emitting
diode. The pressure would generate voltage that could cause the
eyes in a portrait on the note to twinkle. In addition to being
hard to counterfeit, Goldstein says, the feature 'would have a
certain cool factor.'

"Banknotes could conceivably incorporate superelastic and shape-memory
materials, which return to their original shape after being deformed.
Often based on NiTi (a nickel titanium alloy), these materials are
already used in products such as eyeglass frames. A banknote containing
a superelastic wire or thin-foil pattern would spring back to its
original shape after being folded. A note containing a temperature-
sensitive shape-memory feature could be induced to change shape by
the heat from a finger.

"Banknotes could also be printed with temperature-sensitive inks
made of compounds such as thermotropic liquid crystals, which are
used in mood rings. For instance, warming a bill with a finger could
change the color of a portrait of George Washington or cause it to
disappear."

To read the complete article, see: Full Story

  Wayne Homren, Editor

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