Logic at the molecular scale has been exploited to build a keypad lock that opens only when the correct sequence of inputs is applied. Researchers at the Weizmann Institute of Science in Israel explain how they have harnessed the principles of molecular Boolean logic to design and construct a molecular device that mimics the operation of an electronic keypad lock. Keypad locks are now commonplace in buildings, providing entry-exit security, a molecular lock could be used in nanotech encryption devices.
Weizmann organic chemist Abraham Shanzer and colleagues have made a logical connection between molecules and security. They linked two small molecular units that act as fluorescent probes, which are joined via a spacer that can bind iron ions. The first of the molecular probes fluoresces with blue light, the other green. They fluoresce only if the inputs are right. These inputs are the presence of iron ions, acids, bases, and ultraviolet light, rather than the electrical impulses produced by pressing the number buttons on the keypad.
Professor Abraham Shanzer
Shanzer and colleagues David Margulies, Galina Melman, and Clifford Felder, previously showed that the component parts of their molecular keypad can work as logic gates, switching between ON and OFF, the binary 1 and 0 of computation and carrying out arithmetic operations.
The challenge in devising a molecular keypad lock was in making a molecule respond to inputs differently depending on the order they are applied. After all, a keypad lock will open if its password is 324 only if those numbers are entered in that order. Enter 432, 234, or 243 and you stay locked out.
The scientists found that by controlling the opening rate of the logic gate within the reaction time frame, they were able to produce different, distinguishable outputs, depending on the input order. By adding light energy, which also influences the molecule’s glow, they were able to produce a molecule-size device that lights up only when the correct chemical PIN number is introduced. It’s just like a tiny ATM banking machine, says Shanzer. But, could such a molecular device make money?
Shanzer believes this first example of a molecular keypad lock could eventually pay off with new applications in information security and even medicine. Faster and more powerful molecular locks could serve as the smallest ID tags, providing the ultimate defence against forgery, says Shanzer. In the future, molecular keypads might prove valuable, as well, in designing smart diagnostic equipment to detect the release of biological molecules or changes in conditions that indicate disease
Further reading
J. Am. Chem. Soc., 2007, 129, 347-354
http://dx.doi.org/10.1021/ja065317z
Professor Abraham Shanzer
http://www.weizmann.ac.il/oc/shanzer/