Rensselaer Polytechnic Institute (Troy, NY) received U.S. Patent 7,673,521 for its embedded nanotube array sensor and method of making a nanotube polymer composite that can sense its own condition. The material is suitable for jet fuselages and wings and could provide real time sensor information about the conditions of the material. The nanotubes enhance the transport properties of a polymer. The technology is available for licensing from Rensselaer's Office of Technology Transfer.
The process is a scalable inexpensive technique to fabricate flexible carbon nanotube composites according to inventors Pulickel Ajayan, Emer Lahiff, Paul Stryjek Chang Y. Ryu and Seamus Curran. The location and density of conducting channels within the composite can be controlled by soft lithography patterning. The composite can then be used for applications that require conductive channels within a flexible matrix. The method also provides control over the position and density of nanotubes within the composite.
Carbon nanotubes are grown from organometallic micropatterns. These periodic nanotube arrays are then incorporated into a polymer matrix by deposing a curable polymer film on the as-grown tubes. This controlled method of producing free-standing nanotube/polymer composite films may be used to form nanosensors which can provide information regarding a physical condition of a material, such as an airplane chassis or wing, in contact with the nanosensor.
The composite comprising nanotube or nanofiber conductive channels in a polymer or other insulating matrix may be used as an antenna due to the electrical conductivity of the nanotubes or nanofibers, which allow the nanotube or nanofiber conductive channels to wirelessly receive and/or transmit information. The antenna further includes send and/or a receive circuit electrically connected to the carbon nanotubes or carbon nanofibers. For example, standard or custom made send/receive circuits may be used to provide a radio frequency signal emitted by the antenna and/or to decode a radio frequency signal received by the antenna. The send/receive circuit may be powered by a battery, by an AC or DC power source and/or by the RF signal received by the antenna, similar to an RFID tag. It should be noted that only one electrode may be used when the polymer composite is used as an antenna rather than as a sensor.
FIGS. 5A-F are FESEM images of polymer micropatterned substrates for nanotube growth according to an embodiment of the present invention. In FIGS. 5A, 5B and 5C, the darker areas correspond to regions of high organometallic polymer concentration and paler areas represent the silicon oxide substrate. FIGS. 5D and 5E show that after CVD using acetylene, the carbon nanotube growth occurred only on the micropatterned areas of the substrate (i.e., the areas covered with the catalyst template). A close-up image of one of the micropatterned areas in FIG. 5E is shown in FIG. 5F.
The nanotubes enhance the transport properties of a polymer. The presence of the conducting channels is verified by a combination of atomic and electron force microscopy (AFM/EFM). AFM images shown in FIGS. 8A and 8B show the height image data on a scale of 0-10 nm, and the corresponding EFM images (FIGS. 8C, 8D) show amplitude image data on a scale of 0-300 mV. Results shown in FIGS. 8A-D are recorded in tapping mode at a scan rate of 0.500 Hz. It is clear from these images that the height profile of the composite correlates with the position of the conduction channels. The uneven height of the composite surface is believed to be due to the nanotubes protruding from the PDMS surface (dark areas in FIGS. 8A and 8B). The `dots` in the AFM images, which correspond to the nanotube positions, are in the region of 20 nm in diameter.
For more information on this technology please contact the Rensselaer Polytechnic Institute Office of Technology Transfer at otc@rpi.edu or 518-276-6023
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