ImageNASA recently tested the Nano ChemSensor, the first nanotechnology- based electronic device to fly in space. The test showed that the sensor could monitor trace gases inside a spaceship. This technology could lead to smaller, more capable environmental monitors and smoke detectors in future crew habitats. Jing Li, a NASA Ames scientist, is the principal investigator for the test.

NASA Tech Briefs: What is the Nano ChemSensor and why was it developed?

Jing Li: The Nano ChemSensor uses the carbon nanotube-based nano structures to sense different chemicals. The intention of developing this chemical sensor using nano structures is to improve the sensitivity, miniaturize the sensor size, and also try to decrease the power consumption compared to commercially available chemical sensors. The applications of these sensors [are] for environmental monitoring, for leak detection, and also for homeland security and defense applications like warfare agent detection, and at airports for explosives trace detection.

NTB: How much of a power reduction can be achieved compared to conventional sensors?

Li: We put a small gas cylinder – it contained 20 ppm of nitrogen dioxide in nitrogen – and we had three solenoid valves periodically turned on and turned off to release a small quantity of this 20-ppm nitrogen dioxide to the sensor chip, which contains 32 sensors. The results of the test were that some of the sensors do get a response to this 20-ppm nitrogen dioxide. We do see the response peak. That's the result. But then the result is actually that we do see a response, but the response is not as good as on the ground because there is a noise added to the response. We don't know at this moment where the noise comes from. Most likely the noise probably is coming from the data transmission from our device to the main board of the satellite and then downloading to the ground. So it may add the noise during the data transmission.

Right now, we are looking at the data because we do see the main board adding some strange data points to our files. We look at the time sequence, because it's recording the dates, and sometimes there are odd dates coming into the file. Now, we just delete – remove – those strange dates.

For example, we are doing a test in May 2007, and the date jumps to 2000 – some date that is way off from the dates that we are recording right now - so we believe those are data that get added to our data file during the data transmission or data transfer. We do observe actual data points from the main board and we did use some software tools to debug the file in the very beginning in order to make the file readable. So we now see the general response, but we still need to find out some problems with the data set. So, in general we see the data response trends, but not as smooth as we're supposed to see it on the ground.

NTB: What are the future uses or applications of this sensor unit within NASA?

Li: We have some current collaboration with the Kennedy Space Center (KSC). They're actually funding a small amount of money to work on the application for seal leak detection. We've put a lot of effort on NO2 detection. So we are developing this sensor right now for KSC. Another fuel component is hydrozene. We don't have a test facility at Ames, but we send our sensor tips to KSC and they are going to test our sensor to hydrozene at the levels they have concerns for.

NTB: Do you see commercial applications for this technology?

Li: Yes I do. Before we go to the commercial applications, another potential NASA application is for life support systems. Johnson Space Center is looking for a sensor to replace a wet chemical sensor used in space. They are looking for a solid-state chemical sensor to monitor trace gas contaminants in the cabin, either in the International Space Station (ISS) or in the shuttle. And they are looking for this technology to put in the future CEV (Crew Exploration Vehicle).

Currently, there is one engineer from NASA on the design team for the lunar lander who needs to find out more information on our technology to see if he can add this feature to the lunar lander - how much it will cost, how much weight, how big is the volume - and he's going to do these assessments. He also needs to see which chemicals life support needs to accept priority for the life support systems to monitor.

NTB: You said "CEV" before. What is that short for?

Li: CEV is the new-generation vehicle. It's [short for] Crew Exploration Vehicle. Right now NASA is putting a lot of effort on the CEV development plan to replace the shuttle. The shuttle needs to be retired. So, while they are designing this new vehicle they are thinking about integrated features in the vehicle, not like adding onto the shuttle right now because initially when they designed the shuttle, there was no chemical protection, so they added on the capability later. But now when they design the CEV, they are thinking about having this feature in the design.

NTB: So, are there any future commercial [applications]?

Li: I get a lot of interest from industry. For the industry applications, there is one application for environmental monitoring. That's an EPA interest. Another one is for industrial process control.

One typical example is right now, in a candy company, they have a strawberry flavor and a cherry flavor put into the candy. Right now, they just look at the colors, but the colors are very similar, so they taste it or have a human panel just smell the flavor. But they are looking for an instrument to put there so when they switch the product from strawberry to cherry, they wash the product lines until the previous smell, or fragrance, is completely removed – or removed to the level that is acceptable – then go to another product. So they want to have something in-line to monitor this chemical or fragrance - the chemical composition left over on the product line – so they don't need to have a human panel sit there. They just use an instrument to monitor it until it's below the threshold, and then they will automatically order another product to be on this line. Another application is it can be used for raw material inspections. For example, for the chemical industry, that's a simple application for us actually.

Dow Chemical has trucks coming in - they may have a whole truckload of toluene, or tomorrow they will have acetone. Right now, they have people climb a ladder on top of the truck and take a spoon[ful] of the liquid, [send it] off to the lab, and they do the analysis, and then a half-hour or maybe one hour later, when the results come out telling them this is toluene, they will tell the truck driver, 'Okay, drive to that side and dump the toluene into the underground tanks.'

But, if we have the sensor available, it can be made as a handheld so the inspector can have it and they can just smell the tank and [say], 'This is toluene.' Then they just directly ask the driver to drive to the toluene tank. If it is acetone, then they just direct him to the acetone tank. It will make their inspections much easier.

There are a lot of similar applications for the chemical industry or the petrochem industry. Chevron told me they have a complaint from a neighborhood saying they have something released into the air, and it affects people's lives. They want to have these instruments sitting downwind or upwind to see if it's true that this chemical is from their plant, or if it's from somewhere else.

There are a lot of real-world applications. I'm also working with the DHS (Department of Homeland Security) to develop the liquid explosive sensors for airport screening. This is another application for the military or civilians.

I'd like to add that there are three levels of collaboration involved:

  • Within Ames, we (two scientists at Code T) are working closely with Code P where two engineers helped us on the electronics and mechanical design of the flight unit/box and packaged our sensors in it. They also space qualified the nanochem sensor unit (NCSU) with variety tests.
  • Within NASA, Dan Powell and his staff at Goddard Space Flight Center provided us the opportunity to ride on the Midstar-1 and also helped on the integration of our NCSU to the secondary payload of Midstar-1.
  • • Outside NASA, our Code P engineer worked closely with the Midstar-1 PI, Billy Smith at Naval Academy, through out the process of getting the requirements and interface the NCSU with Midstar-1.

I would like to acknowledge their critical contribution to this success and all levels of management support.

For more information, contact Jing Li at This email address is being protected from spambots. You need JavaScript enabled to view it..

NASA Tech Briefs Magazine

This article first appeared in the August, 2007 issue of NASA Tech Briefs Magazine.

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