Strain-based Electrical Properties of Systems of Carbon Nanotubes Embedded in Parylene. Jon A. Brame1, Johnathan Goodsell1, Stephanie A. Getty2 and David Dean Allred1; 1Physics and Astronomy, Brigham Young University, Provo, Utah; 2Materials Engineering Branch, Code 541, NASA -- Goddard Space Flight Center, Greenbelt, Maryland.
In an effort to create a micro-scale, strain-based sensor system, we will investigate and discuss the unique electromechanical properties of single walled carbon nanotubes (SWCNT). The remarkable strain-based change in resistance of SWCNTs has been previously measured individually using atomic force microscopy (Tombler et. al, Nature vol. 405, p. 796, 2000). We report the application and utilization of this property in an ensemble array of nanotubes on flexible substrates. Our SWCNTs were grown on a silicon wafer substrate, using a chemical vapor deposition process with methane and ethylene as the carbon sources, and a variety of catalysts. Gold electrical contacts (100 nm) were shadow evaporated on top of the nanotubes, and the entire sample was coated with parylene (~25Ám). The parylene and silicon substrate were subsequently etched from the back using standard dry and wet etching techniques, effectively transferring the SWCNT device to a flexible polymer substrate. To test the resistance of the ensemble of nanotubes, the structure was mounted to a probe station using micromanipulators which could stretch or compress it and measure its (two-point probe) resistance throughout. We will discuss the results and their application to future instruments for space and planetary science. Additionally, we compare the use of iron nitrate versus thin film iron catalysts, and discuss the differences between this CVD growth process and commercially available carbon nanotubes (buckypaper).