New microprocessor runs on thin air

There's no shortage of ways to perform calculations without a standard electronic computer. But the latest in a long lineMovie Camera of weird computers runs calculations on nothing more than air.

The complicated nest of channels and valves (see image) made by Minsoung Rhee and Mark Burns at the University of Michigan, Ann Arbor, processes binary signals by sucking air out of tubes to represent a '0', or letting it back in to represent a '1'.

A chain of such 1's and 0's flows through the processor's channels, with pneumatic valves controlling the flow of the signals between channels.

Valve computer:

Each pneumatic valve is operated by changing the air pressure in a small chamber below the air channel, separated from the circuit by a flexible impermeable membrane. When the lower chamber is filled with air the membrane pushes upwards and closes the valve, preventing the binary signal flowing across one of the processor's junctions.

Sucking out the air from the chamber reopens the valve by forcing the membrane downwards, letting the signal move across the junction.

The two researchers used the valve-controlled channels to produce a variety of logic gates, flip-flops and shift registers, which they linked together to create a working 8-bit microprocessor. That means that the longest discrete pieces of data it can handle are eight binary digits long, like the processors used in 1980s consoles such as the Nintendo Entertainment System.

It's even possible to watch the pneumatic components in action, because the valve membranes reflect light strongly whenever they are forced downwards

But the air processor is far from just being a computational curiosity, it has the potential to improve the "lab-on-a-chip" devices tipped to automate complex chemistry tasks and improve disease testing, DNA profiling and other lab jobs.

These pocket-scale microfluidic devices are yet to be much practical use, because they typically require a large number of bulky and expensive off-chip components to control their operation.

Using logic circuits is one way to bring most of those controls onto the lab-on-a-chip itself and reduce running costs. But because many microfluidic systems have no electronic components, adding standard electronic valves to the device would require a new fabrication process.

Many microfluidic systems use pneumatic valves to control liquid flow, so adding the pneumatic control circuits should be relatively simple and inexpensive, Although the device still requires an off-chip vacuum source to operate, the volume of the microprocessor is so small that the required vacuum can be generated by a hand pump.