The team has only managed the feat on nail clippings so far,
but they hope the process could one day be used to securely carry
information on fingertips.Yoshio Hayasaki of the University of
Tokushima and his colleagues said a single fingernail could accommodate
approximately 800 kilobytes of data. That would not provide room for a
high-resolution photo, but would be enough to store basic
identification information.Hayasaki and his team achieve the
feat by using a laser that delivers very short pulses of infrared light
onto a finely focused spot, they report in Optics Express1. When
the nail is illuminated with blue laser light to excite fluorescence,
recorded dots appear brighter than the material surrounding them,
allowing the information to be read under a microscope.Because
it is possible to adjust the depth of the writing, they say several
layers of information can be superimposed within a single slab.