Kimberly Patch in TRN:
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 fingernail material.
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 replaced.