Most of us carry a number of credit/ATM cards, cash, and several other cards (driving license, bank card, library cards and so on). It makes our wallet bulky, and there is always the danger of losing the wallet! Now, thanks to researchers at Tokushima University (Yoshio Hayasaki and colleagues), secure optical data storage could soon literally be at our fingertips:):).
The researchers have discovered that data can be written into a human fingernail by irradiating it with femtosecond laser pulses. Capacities are said to be up to 5 mega bits and the stored data lasts for 6 months - the length of time it takes a fingernail to be completely replaced.

Etching on a fingernail (Courtesy: PhysicsWeb)The approach is simple. The team uses a femtosecond (10^-15 seconds) laser system to write the data into the nail and a fluorescence microscope to read it out. During the writing, the fluorescence of the nail increases in the irradiated regions. The fluorescence microscope is able to read this difference in intensity, while reading the data from the nails:):).
Each "bit" of information has a diameter of 3.1 microns (10^-6 meters) and is written by a single femtosecond pulse. A motorised stage moves the nail to create a bit spacing of 5 microns across the nail and a depth of 20 microns between recording layers. Considering that the nail fragment used was about 2x2x0.4 cubic millimetres in size, a total of around 1560 KiloBytes could be stored. More data could be stored if the full human nail were used!
The team is now focussing on reading to and writing from a nail that is still attached to the finger. This means that the team also has to find ways to compensate for the movement of the finger. Once this issue is sorted out, we could have our credit card numbers, and other important data, right at our finger-tips:D:D.