Microfluidics go nonlinear

Researchers from the California Institute of Technology and the University of California at San Diego have constructed computer-logic-like circuits that control the flow of fluid through a chamber rather than the flow of electricity through a solid.

The microfluidic circuits could eventually be used to deliver constant flows of medicine to specific points in the human body and to control other microfluidic devices.

The key to the circuit-like behavior is an elastic polymer fluid that has non-linear properties similar to those of electronics components. In a linear system the output is proportional to the input; nonlinear output, however, increases or decreases at a different rate than the input.

The fluid circuits have different-shaped channels that cause the molecules of the elastic fluid to align or scramble, changing the fluid's viscosity and therefore its flow rate.

The researchers have constructed a pair of prototype devices. One produces a constant flow despite changes in fluid pressure. The second switches between two output channels without using valves. The output channels can represent a 1 and a 0, respectively, and a string of the devices can store the binary numbers used in computing.

The work appeared in the May 9, 2003 issue of Science.