Chemical Calculators - Supercomputer Molecules

Chemical Calculators - Supercomputer Molecules

Prasanna 'AP' de Silva and Nathan McClenaghan at Queen's University, Belfast have used molecules that switch on and off depending on a chemical signal, and can produce a tiny burst of light representing a binary number 1. Such molecules can work as the equivalent of the tiny logic gates on a silicon chip, making decisions on each bit of computer information that passes through them. By running them together the researchers can carry out arithmetic operations.

Normally, a vast array of millions of transistors etched on to a silicon chip is at the heart of a computer, but chips are like whole cities on the molecular scale and when real estate is getting tighter and tighter it is time for the molecular architects to step in.

'The extension of information processing and computation to the molecular level will only be possible when molecular logic gates are available,' according to Vincenzo Balzani of Bologna University. He believes chemists can design and construct molecules to do the work of silicon chips but in a much smaller space and far faster.

There are several different logic gates used in computing. For instance, an 'AND' gate gives an 'on' or '1' output when both its inputs are '1'. An 'OR' gate, is only 'on' or '1' when its inputs are '1' or '0'. The slightly bizarre 'XOR' (eXclusive OR) gate acts like a 'spot the difference' unit giving no output if both inputs are 1s or 0s but a '1' if they are '1 and 0' or '0 and 1'. The NOT, OR, INH, and NOR gates and many others all work together to do addition, subtraction, multiplication, and division. With those mathematical functions, you can carry out any conceivable computer process - from displaying a single word on-screen to rendering a multimedia web site. Computation always reduces to maths.

De Silva and his colleagues previously built molecular versions of several logic gates, including the AND and XOR. The gates are based on tiny claw- shaped molecules that trap different ions. They then use these ions to represent binary 1's. When two different ions are present (a calcium and a hydrogen) the claw molecule glows blue, representing a '1' output. With no ions present the molecule stays switched off, there is no glow, so the output is 0. The XOR molecule works similarly but lights up only when the two inputs are different.