Just as the electronic transistor became the main component of the microchips that drive today's computers, so could the nanofluidic transistor become the foundation of microscopic labs that replace the giant robotic workstations now used by industry to analyze DNA and other ingredients of life.

The chips also might function as reactors that generate hard-to-make drugs and other compounds, the UC-Berkeley team predicted.

"You could imagine planning the movement of these molecules on a single-molecule level to let them react at certain points in a device in very specific ways," Peidong Yang, associate professor of chemistry and research team member, told UPI's Nano World.

Nanofluidic devices can position thousands of nanoscale pipes onto a square inch. Scientists mix the liquids inside the devices much as chemists might combine beakers of solutions or biologists mix genes with enzymes - except the process accomplishes the kind of work current industrial approaches tackle with machines that would fill a railroad car and require much more expense and labor.

The chips promise as much impact on medicine, biology and chemistry as electronic chips have had on the space program and the Internet. For instance, a nanofluidic chemical analysis device, in theory, could take the contents of 10 cancer cells and pull out protein markers that could reveal the best way of attacking the cancer, Yang said.

"This is an ideal way to open up cells and identify the proteins or enzymes inside," he explained. "An enzyme profile would tell doctors a lot about the kind of cancer, especially in its early stages when there are only a few cells around."

Current microfluidic devices often use valves between the pipes that can become stuck, but the nanofluidic transistor "is like a valve, but you use electricity to open or close it," explained Arun Majumdar, mechanical engineer and team member.

The team constructed a 35-nanometer-high channel between two silicon-dioxide plates and then filled the channel with water and potassium-chloride salt. By applying an electric current across the channel by means of electrodes attached to the plates, they shut off the flow of potassium ions through the water.

Yang said the team also has created a version of the transistor using 20-nanometer-wide silicon-dioxide nanotubes.

The researchers demonstrated they could manipulate charged DNA fragments with their silicon-dioxide transistor, which in principle allowed them to sort and sequence genes. Majumdar and Yang said the nanofluidic transistor could, in theory, perform biomolecular manipulation, sensing down to the level of a single molecule.

One major advantage of nanofluidic transistors, Majumdar said, is they can be made using the same technology as in the semiconductor industry. The devices could be integrated with electronics on a single silicon chip, with the electronics controlling the operation of the nanofluidics.

"One major challenge that still exists here is the assembly and integration of these transistors in a massively parallel manner," said electrical and biomedical engineer Rashid Bashir at Purdue University in West Lafayette, Ind., who did not participate in this study.

"But this is a very unique and powerful technique, and there's a lot of potential ability for them to integrate these transistors in a large array."

Yang said nanofluidic transistors could help create a novel nanofluidic computer.

"Using molecules to process information gives you a fundamentally different information-processing device," he explained.

The team is working on understanding the surface effects inside the nanochannels and on reducing the voltage the transistors need to shut off - currently 75 volts, far too high for any of today's circuitry.

Charles Choi covers research and technology for UPI Science News. E-mail: [email protected] Community
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