Thursday, June 05, 2008

A Tiny Sensor Simply Made

A nanoscale biosensor that can detect minute amounts of pathogens could come to market this year.

By Brittany Sauser

Detecting biohazards: A prototype of NASA’s nanotechnology-based biosensor has been licensed to Early Warning. The company is incorporating the technology into a device that will test for common and rare strains of microorganisms associated with waterborne illnesses in municipal water systems. Credit: NASA

Researchers at NASA Ames Research Center have developed a nanotechnology-based biosensor that can detect trace amounts of as many as 25 different microorganisms simultaneously and within minutes. The researchers make the biosensors by growing carbon nanofibers--a material with the same properties as carbon nanotubes but with a slightly larger diameter--using a process similar to the one employed to fabricate computer chips.

"By using the same reactor technology the semiconductor industry uses, we have created an innovative approach to manufacturing tiny sensors," say Meyya Meyyappan, the chief scientist for the biosensor project.

While NASA plans to eventually use the sensor to detect the presence of life on other planets, it has licensed the technology to Early Warning, a company based in Troy, NY, that develops systems to monitor biohazards. The company's president, Neil Gordon, says that the first application for the sensor will be for water-quality monitoring, and a prototype of the technology will be tested at a series of demonstration sites this summer. Early Warning plans to have a commercial product by the end of the year.

It has been known for almost a decade that carbon nanotubes and nanowires make good sensors, says Mark Reed, a professor of electrical engineering and applied physics at Yale University. But, says Reed, only in the past couple of years have research groups started to explore an integrated approach--electronics and biology--to build biosensing devices. Reed's group is among those using an integrated approach to build nanoscale sensors based on carbon nanowires. Harvard researchers led by chemist Charles Lieber were the first to show virus detection and the detection of early signs of cancer through semiconducting nanowires. Other academic groups, such as those at California Institute of Technology, the University of Southern California, and Boston College, are doing similar work.

Such biosensors, which are based on the detection of electrical signals, offer several advantages over more conventional optical technologies. For one thing, the electronic and electrochemical approaches do not require the use of florescent chemical tags, says Charlie Johnson, a professor in the department of physics and astronomy at the University of Pennsylvania. Electrical signals are also easier to measure than optical ones, he says.

NASA, however, is one of the few groups using carbon nanofibers to make biosensors. Carbon nanofibers are easier to work with than nanotubes are, and they can be grown on a silicon substrate in the exact structure that researchers desire, says Meyyappan.

Indeed, the real challenge to making electronic-based biosensors into products is not which material performs the best, but how they will be mass-produced, says Reed. "I am impressed by NASA's work, and they have very nice results," he says.