Miniature keypad locking

A team of scientists at the

has created a molecule that can function as an ultra-miniaturised version of a keypad locking mechanism.

Keypad locks, such as those for preventing car theft, allow an action to take place only when the right password is entered via a series of numbers punched in a pre-set sequence. Now, a team of scientists at the Weizmann Institute of Science has created a molecule that can function as an ultra-miniaturised version of a keypad locking mechanism.

The molecule, synthesised in the lab of Prof. Abraham Shanzer of the Organic Chemistry Department, is composed of two smaller linked fluorescent probes separated by a molecular chain to which iron can bind. One of these probes can shine bright fluorescent blue and the other fluorescent green, but only if the surrounding conditions are right. These conditions are the keypad inputs. Rather than the electric pulses of an electronic keypad, they consist of iron ions, acids, bases, and ultraviolet light.

Shanzer and his group have demonstrated in the past that such molecules can be used as logic gates, such as those that form the basis of computer operations. As opposed to electronic logic gates, in which electrical switches flip on and off, the team’s molecules, with various combinations of chemical and light inputs, can switch between colours and light intensities to perform arithmetic calculations.

The challenge in creating a keypad lock was in generating sequences that can be distinguished one from another. Entering the sequence 2+3+4 will yield the same result as 3+4+2 on a calculator, but a keypad lock set to one password (234) won’t open for the other (342).

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 molecules’ glow, they were able to produce a molecule-size device that lights up only when the correct chemical ‘passwords’ are introduced.

‘It’s just like a tiny ATM banking machine,’ said Shanzer.

Although these minuscule keypads are not likely to become a practical alternative to today’s anti-theft devices, Shanzer believes this first example of a molecular keypad lock will lead to new ideas and inventions in other areas such as information security and even medicine.

‘Faster and more powerful molecular locks could serve as the smallest ID tags, providing the ultimate defence against forgery,’ he said.

In the future, molecular keypads might also prove valuable in designing ‘smart’ diagnostic equipment to detect the release of biological molecules or changes in conditions that indicate disease.