This document discusses using femtosecond laser pulses to store data in human fingernails. Researchers have demonstrated storing up to 5 megabits of data in fingernails that can be read for up to 6 months as the nail grows out. Data is written by focusing femtosecond laser pulses inside the nail, causing structural changes in keratin proteins detected as increased fluorescence using a microscope. This allows for high density data storage of 2 gigabits per cubic centimeter. The technique provides a secure way to store personal identification or other sensitive data within the body.

1. Data Storage on Fingernails
Presented By:
Vishal Anand
Secure optical data storage could be at your
fingertips

2. Contents
1. Introduction
2. Basic approach
3. Apparatus used
4. How data is stored on fingernails
5. Data reading from nails
6. The optical setup for reading out the bit data
7. Other parts of human body in which data
can be stored
a) The lens of the eye
b) Teeth
c) Hair
8. Data Storage at Different Levels
9. Advantages
10.Conclusion

3. Introduction
 Yoshio Hayasaki of Tokushima University (Japan) and his colleagues discovered that data can be
written into human fingernail while ensuring data security.
 Japanese researchers are using femtosecond laser pulses to write data into human fingernails.
 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.

4. Basic Approach
 Use a femtosecond laser system to write the optical data into the nail.
 Use 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.
 The multilayer technique offers a data storage density of 2 Gb/cm3.

5. Apparatus Used
Femtosecond Laser Fluorescence Microscope

6. How Data is Stored on Fingernail?
 When the femtosecond laser pulses (UV) strike the
sample, structural changes occur at the focal point.
 The researchers believe that multiphoton absorption
and a micro explosion cause keratin protein in the
fingernail to denature and the fluorescence to increase.
 Each "bit" of information has a diameter of 3.1 microns
and is written by a single femtosecond pulse.
 This change occur due to ionization of molecules .

7. Data Reading from Nails
 An fluorescence optical
microscope containing a filtered
xenon arc lamp excites the
fluorescence and reads out the
data stored at the various depths.

8. The Optical Setup for Reading Out The Bit
Data
 Fluorescence microscope consisting of a
 Xenon arc lamp as an exciting light source
 Filter blocks. Each of the filter blocks consists of an excitation filter which is a band-pass filter

9. Data Storage at Different Levels

10. Advantages
 Person’s authentication
 Does not suffer from problems such as theft, forgery, or loss of recording media
 Highly secure data transportation
 Can be used for intelligence
 Don’t need to carrying around a large number of cards, money and papers

11. Other Parts of Human Body in Which Data
Can be Stored
 The lens of the eye
 Teeth
 Hair

12. Conclusion
We have demonstrated an increased fluorescence intensity at the structural change inside a human
fingernail produced by a focused femtosecond laser pulse. The fluorescence intensity was higher than
the surrounding auto-fluorescence intensity of the fingernail. The structural changes, whose
geometrical shape drastically depends on the irradiated pulse energy, are observed as a dark region by
using a microscope with transmission illumination. The increased fluorescence intensity was
observed in the dark region. The spectrum of the increased fluorescence coincided with the auto-
fluorescence spectra of the fingernail. The increased fluorescence intensity was also observed in a
fingernail heated in a drying oven. It is suggested that the increased fluorescence of the structure is a
result of a local denaturation the keratin protein caused by heat generated by the femtosecond laser
pulse irradiation.
Furthermore, we demonstrated that fluorescence can be observed for up to 6 months, corresponding
to the time required for a nail to grow from root to tip. Under these recording conditions, a recording
density of 2 Gbit/cm3 is achievable.

13. References
 Takita, A., M. Watanabe, H. Yamamoto, S. Matsuo, H. Misawa, Y. Hayasaki, and N. Nishida,
“Optical bit recording in a human fingernail,” Jpn. J. Appl. Phys., Vol. 43, No. 1, 168–171, 2004.
 Hayasaki, Y., H. Takagi, A. Takita, H. Yamamoto, N. Nishida, and H. Misawa, “Processing
structures on human fingernail surface by a focused near-infrared femtosecond laser pulse,” Jpn.
J. Appl. Phys., Vol. 43, No. 12, 8089–8093, 2004.
 Takita, A., H. Yamamoto, Y. Hayasaki, N. Nishida, and H. Misawa, “Three-dimensional optical
memory using a human fingernail,” Optics Express, Vol. 13, No. 12, 4560–4567, 2005.
 Ichikawa, T., Y. Hayasaki, K. Fujita, K. Nagano, M. Murata, T. Kawano, and J. R. Chen,
“Femtosecond pulse laser-oriented recording on dental prostheses,” Dental Materials J., Vol. 25,
No. 4, 733–736, 2006.
 Takita, A., Y. Hayasaki, and N. Nishida, “Femtosecond laser processing system with target
tracking feature,” Journal of Laser Micro/Nanoengineering, Vol. 1, No. 3, 288–291, 2006.

14. Thank you
Vishal Anand
Q&A