Nano Sensors for Chemical Detection

A silicon-based sensing chip consists of 64 nano sensors, and is less than one square centimeter. (NASA Ames/Dominic Hart)
The 2012 NASA Government Invention of the Year was awarded to a tiny sensor that detects chemicals in the air. The technology, titled “High Sensitive, Low Power and Compact Nano Sensors for Trace Chemical Detection,” was invented by Jing Li and Meyya Meyyappan of NASA’s Ames Research Center in Moffett Field, CA, and Yijang Lu of the University of California, Santa Cruz.

Electronic sensors, made from carbon nanotubes, estimate one or more unknown parts of a gas. The sensors are inexpensive, lightweight, and consume very little power. A typical sensor includes a set of comb-shaped metal microelectrodes — fabricated by photolithography — on an electrically insulating substrate.

The sensors have been deployed by NASA to detect trace gases in the crew cabin on the International Space Station. Other federal agencies are using sensors based on this technology to detect trace gases in various environments.

Specific applications for which the innovative devices have been tested and used include trace chemical detection in planetary exploration, air monitoring, leak detection, and hazardous agent detection using cell phones. Potential future applications may include environmental monitoring, industrial process monitoring and control, and biomedical diagnosis.

“We’re very pleased to have Ames inventiveness recognized with this award for the third consecutive year,” said S. Pete Worden, NASA Ames center director. “With this invention, our people have basically created the insides of a tricorder, and based on the uses we’ve already demonstrated, I can’t wait to see the fantastic applications that NASA and industry are going to devise for it.”

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Catalyst System

A cordierite substrate, coated with a catalyst material. (NASA)
A team at Langley Research Center in Hampton, VA, was presented with the 2012 NASA Commercial Invention of the Year. The technology was invented by Jeff Jordan, Jacqueline Schryer, Patricia Davis, Neal Watkins, Donald Oglesby, Bradley Leighty, and the late David Schryer.

The team’s creation, entitled “Methodology for the Effective Stabilization of Tin Oxide-Based Oxidation/Reduction Catalysts,” stabilizes a catalyst in virtually any application that requires the removal of toxic compounds, including carbon monoxide. Unlike a conventional catalyst, the technology has low, near-room-temperature oxidation capabilities that are maintained up to temperatures greater than 800 °C, or about 1472 °F. Current catalyst systems cannot change the state of carbon monoxide (CO) and hydrocarbons (HC) in such a wide range of temperatures.

The technology is capable of removing other volatile compounds, such as formaldehyde and nitrogen oxides, from exhaust streams. Traditional technologies employ filters to remove contaminants like CO and HC, which become saturated and have to be replaced. The invention, however, can be used for longer time periods since the molecules are converted to carbon dioxide, which requires less system maintenance.

The Langley methodology removes pollutants from environments such as ground and flight vehicle engines that operate on fuels, including diesel, natural gas, and alcohol fuels.

“The fact that it can operate over a very wide temperature range lends itself to applications from lawn mowers to, potentially, jumbo jets,” said Neal Watkins, one member of the Langley team.

The process could be valuable for mining, power generation, construction, loco motive, forestry, and marine purposes. It may also be used in personal safety equipment, as well as detection schemes, to produce low-cost chemical sensors for the trace detection of pollutants. The methodology has immediate aerospace applications as well, including green aircraft, cabin and habitat air purification, and other trace contaminant elimination from life support systems.

The new production method incorporates at least one additional metal oxide species. The oxides stabilize the active tin oxide layer during a high-temperature operation in a reducing environment, such as vehicle exhaust.

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