Electrostatic Self Assembly of Virgin Carbon Nanotubes Between Two Electrodes for Sensor and Transistor Applications

摘要

Using electrostatics and liquid toner techniques from copier/laser printer industry, we are able to "self assemble" virgin carbon nanotubes from dispersions in naphtha like liquids. These assemblies are created between two electrodes on a dielectric surface with gaps between electrodes that range up to 2 mm. The channel widths extend to 6 to 10 mm. The dielectric surfaces include glass/epoxy semi-rigid boards (PWB's), Aramid fiber reinforced Teflon, and soda lime glass. By virgin nanotubes we mean single wall nanotubes ("SWNT") where no surface functionality, per se, has been added. This means that no wetting agents, no surfactants, nor any poly-electrolytes (charge directors) were added to the liquid. The self assembly techniques shown here also work with multi-wall tubes but they are not used for sensors and transistors. The naphtha like liquids are very pure linear, aliphatic hydrocarbons synthesized from gaseous materials. They are a close approximation to the odorless mineral spirits used to thin alkyd paints by the homeowner. Though SWNT's can be made into traditional liquid toners possessing an electrochemical charge, these formulations require the application of a functional coating on the SWNT. Regrettably, these functional coating degrade the performance of the SWNT material. For this effort we chose and approach that uses the fibers in the virgin state, no coatings of any kind for best sensor performance. After completion these sensor substrates receive a final functional coating, unique to the chemical or bio-agent to be detected, We will discuss the theory behind our fiber assembly processes and show samples of typical parts we've manufactured multiple times. In addition we hope to have a video presentation of the process. Beyond the obvious application of building sensors, the process can also be applied to assemble the channel of a high performance field effect transistor for use in phased array radars and various types of backplanes for flat panel displays.