A new kind of chemical processing

A transistor-like structure which combines fluid dynamics and electronic design could form the basis of diagnostic equipment and even microprocessor-like arrays, according to engineers from the University of California at Berkeley. The so-called nanofluidic transistor controls the flow of small amounts of liquids through fine channels with electrical charges, and can be used for sensing, sorting and sequencing biological molecules.

‘A transistor is like a valve, but you use electricity to open or close it,’ explains Arun Mjumdar, professor of mechanical engineering. ‘Here, we use a voltage to open or close an ion channel. Now we’ve shown we can make this building block, we can hook it up to an electronic chip to control the fluidics.’

The model ‘transistor’ consists of a 35nm channel between two silicon dioxide plates, filled with a solution of potassium chloride in water. A voltage across the channel acted like a gate voltage in a conventional transistor, shutting off the flow of potassium ions. A similar system could be used to shuttle charged proteins through a channel lined with fluorescent antibodies for detecting or sensing, or for sorting fragments of DNA.

‘It might seem a little far-fetched, but we’re thinking about whether we can do the same thing with nanofluidic transistors as we can currently do with MOSFETs,’ says Peidong Yang, another of the researchers. MOSFETs, metal oxide semiconductor field effect transistors, are an essential component of high-speed microprocessors. ‘Using molecules to process information gives you a fundamentally different information processing device.’

The next stage of the research will focus on the surface effects inside the microchannels, and designing channels which can be closed with low voltages. 'We want to be the first to build integrated circuits with just three transistors able to do sorting and eluting, just as a two- or three-bit processor can do multiplexing and addressing,’ says Majumdar.