Nanotechnology-based flexible hydrogen sensors
Researchers from U.S. Argonne National Laboratory have developed flexible sensors for hydrogen vehicles. These sensors will be cheaper than previously designed hydrogen sensors because they will use only palladium nanoparticles instead of pure palladium. But they will be as efficient and could be used in many applications, like in vehicles, aircraft and portable electronics. They could even be used to detect a 'leakage of hydrogen caused by tiny pinholes in the pipe of a space shuttle.'
You can see above one of these flexible hydrogen sensors (Credit: Argonne National Laboratory). Here is a link to a slightly larger version of this picture.
Here are some details about the fabrication of these flexible sensors. "Yugang Sun and H. Hau Wang, researchers in Argonne's Center for Nanoscale Materials and Materials Science Division, respectively, fabricated the new sensing devices using a two-step process separated by hig] h and low temperatures. First, at around 900 degrees C, researchers grow SWNTs [single-walled carbon nanotubeson a silicon substrate using chemical vapor deposition. Then, researchers transfer the SWNTs onto a plastic substrate at temperatures lower than 150 degrees C using a technique called dry transfer printing.
According to the scientists, "these sensors exhibit excellent sensing performance in terms of high sensitivity, fast response time and quick recovery, and the use of plastic sheets reduces their overall weight and increases their mechanical flexibility and shock resistance. The sensors are also able to be wrapped around curved surfaces, and this proves useful in many applications, notably in vehicles, aircraft and portable electronics."
As I wrote above, these sensors could be used to improve the security on space shuttle flights. "The leakage of hydrogen caused by tiny pinholes in the pipe of a space shuttle, for example, could not be easily detected by individual rigid detectors because the locations of pinholes are not predetermined," said Sun. "However, laminating a dense array of flexible sensors on the surfaces of the pipe can detect any hydrogen leakage prior to diffusion to alert control units to take action."
Finally, how can we compare previously rigid hydrogen sensors and these new flexible ones in terms of performance? "Flexible hydrogen sensors show a change of 75 percent in their resistance when exposed to hydrogen at a concentration of 0.05 percent in air. The devices can detect the presence of 1 percent hydrogen at room temperature in 3 seconds. Even after bending -- with a bending radius of approximately 7.5 mm -- and relaxing 2,000 times, the devices still perform with as much effectiveness."
Sources: Argonne National Laboratory news release, July 31, 2007; and various websites
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