MIT researchers are using bubbles to do computation on "labs-on-a-chip." The novel processor is a microfluidic chip containing a network of hair-thin plumbing pipes with nanofliters of fluid pumped through them. The architecture enables the presence or absence of a bubble to represent a single bit of information. Professor Neil Gershenfeld and his colleagues used nitrogen bubbles in water, but apparently oil and water and other fluids that don't mix would also be fine. From the MIT News Office:
Controlling chemical reactions will likely be a primary application for the chips, according to the researchers. It will be possible to create large-scale microfluidic systems such as chemical memories, which store thousands of reagents on a chip (similar to data storage), using counters to dispense exact amounts and logic circuits to deliver them to specific destinations.
Other applications include combinatorial synthesis of many compositions at the same time, programmable print heads that can deposit a range of functional materials, and sorting biological cells.
The speed of operation is about 1,000 times slower than a typical electronic microprocessor, but 100 times faster than the external valves and control systems used in existing microfluidic chips. Gershenfeld and Prakash anticipate that its invention will allow existing circuit designs (and designers) to work in the domain of microfluidics.