Fingernail storage is a method of writing data onto a human
fingernail using a pulsed laser. The fluorescence of the nail,
when exposed to ultraviolet (UV) light, is increased at points
where data is written. Data can be read from the fingernail
using a microscope while irradiating the nail with UV energy.
Recent experiments with fingernail storage, conducted by Yoshio
Hayasaki of Tokushima University (Japan), have involved small
regions of a single nail, measuring approximately two
millimeters (mm) square. A pulsed laser is used, at a wavelength
of 800 nanometers (nm), to write the data onto the nail. Each
data bit measures approximately 0.003 millimeters (mm) in
diameter. Individual data bits are spaced 0.005 mm apart, in
three layers at depths of 0.04, 0.06, and 0.08 mm within the
nail. Fingernail storage has a limited life because human nails
grow out. The average human fingernail is completely replaced by
the body every six months, assuming the nail is clipped short at
regular intervals. Fingernail stora