Technology Research News
the stuff of spy fiction.
Researchers from the University of Tokushima and Hokkaido University
have demonstrated that it is possible to read data written into a human
fingernail using a laser, much like information is written on a rewritable
compact disc. The data is read using an optical microscope.
The researchers' original idea was to find a way to write data directly
to some part of the human body for security purposes. They considered hair,
teeth and skin before settling on fingernails.
The researchers' proof-of-concept demonstration involved recording
and reading numbers, Japanese characters, and an English word in dot patterns
on the inside of a human fingernail.
The method could be used for personal authentication, said Yoshio
Hayasaki, an associate professor of optical science and technology at the
University of Tokushima. It could also be used in conjunction with biometric
authentication like fingerprints and vein patterns, he said.
The researchers tried several technologies before finding a method
of writing data into fingernails so that it can be easily read, said Hayasaki.
They wrote dot patterns into a fingernail using a laser that emitted
pulses lasting a few million billionths of a second. The molecules of the
fingernail that were hit by the laser became ionized, and because ionized
molecules repulse each other, they caused a tiny explosion. The explosion
changed the structure of the material at that location by decomposing the
keratin protein molecules located there. These areas can be read because
they fluoresce, or absorb and emit light, at a higher rate than the surrounding
The tiny explosion areas are about three microns wide and 20 microns
deep, and can be written five microns apart. The researchers recorded and
read three layers of these dots, at 40, 60 and 80 microns below the nail
surface. The dots are visible under blue light, and thus can be read using
a microscope. A micron is one thousandth of a millimeter.
Two gigabits of data can be written per cubic centimeter of fingernail
using these size dots. Today's compact discs hold about 5.6 gigabits of
data. A practical fingernail recording area of 5 millimeters by 5 millimeters
by one tenth of a millimeter deep would hold 5 megabits of data, or about
300 pages of text.
The researchers' proof-of-concept samples could still be read 172
days after recording. This is probably the practical limit of fingernail
storage because after six months a fingernail has grown enough to be completely
The researchers' next step in making the method practical is to
find a safe, inexpensive way to write data. "The important things for practical
use are to ensure safety and reduce costs," said Hayasaki. "We need [a]
more sophisticated laser processing system to write data in the nail on
a finger, because the finger moves," he said.
The researchers are in the process of developing a femtosecond laser
writing system that can compensate for movement as it is recording data,
The method could be practical within three years, said Hayasaki.
Hayasaki's research colleagues were Akihiro Takita, Hirotsugu Yamamoto
and Nobuo Nishida at the University of Tokushima, and Hiroaki Misawa at
Hokkaido University. The work appeared in the June 13, 2005 issue of Optics
Express. The research was funded by the University of Tokushima, the
Mazda Foundation, the Secom Science and Technology Foundation, the Telecommunications
Advancement Organization of Japan, and the Japanese Ministry of Education,
Science, Sports and Culture.
Timeline: 3 years
Funding: Corporate, Government
TRN Categories: Data Storage Technology; Optical Computing,
Optoelectronics and Photonics
Story Type: News
Related Elements: Technical paper, "Three-dimensional Optical
Memory Using a Human Fingernail," Optics Express, June 13, 2005
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