A team in Japan has invented a means of storing digital data in your fingernails:
The team’s approach is simple: use a femtosecond laser system to write the data into the nail and a fluorescence microscope to read it out. The key to reading the data out is that the nail’s fluorescence increases at the point irradiated by the femtosecond pulses.
Initial experiments were carried out on a small piece of human fingernail measuring 2 x 2 x 0.4 mm3. The writing system comprises a Ti:Sapphire oscillator and Ti:Sapphire amplifier. Pulses of less than 100 fs at 800 nm are then passed through a microscope and focused to three set depths (40, 60 and 80 microns) using an objective lens.
Each “bit” of information has a diameter of 3.1 microns and is written by a single femtosecond pulse. A motorized stage moves the nail to create a bit spacing of 5 microns across the nail and a depth of 20 microns between recording layers.
An optical microscope containing a filtered xenon arc lamp excites the fluorescence and reads out the data stored at the various depths. “We regulate the focus with the movement of the microscope objective,” explained Hayasaki. “The distance between the planes is set to prevent cross-talk between data stored at different depths.”
Capacity is around 5 megabits (roughly 0.625 megabytes) of storage that will last around 6 months, which is the average time for your fingernail to be completely replaced. If you use all 20 finger and toenails you’d have a maximum storage potential of 12.5 megabytes or so. Not sure how useful that would be, but the inventors see possible applications for personal identification or biometrics. I wonder how well it deals with aberrations in a fingernails such as one I have myself that I call my “racing stripe.” My right thumbnail has a number of dark vertical lines in one part of the nail that are the result of some minor nerve damage when I was younger and would probably play hell with the laser. Not that it matters, I keep my fingernails trimmed down pretty obsessively because I can’t type very well if I don’t so I’d be deleting data on a regular basis. Still, it’s pretty nifty.