Day 2 of the 2012 TechConnect World Summit, Expo & Showcase opened with fifteen parallel sessions ranging from printed and flexible electronics to device modeling to green chemistry and water to nanotechnology for cancer diagnostics. The unifying theme for this conference is promising technology in search of funding and the opportunity for market validation.
Liyong Diao of Brewer Science described the fabrication and characterization of CNT inductors on flexible plastic substrates. The Brewer operation in Springfield, MO is focused on materials & process development for printed electronics. Both SWCNT and MWCNT have a maximum current density, electron mean free path and thermal conductivity several orders of magnitude higher than copper. The Brewer material is applied as a spray suspension of CNT, and thin films had a sheet resistance <1Ω/square. Multiple spray/dry cycles are used to build up film thickness to the target 10µm. The CNT film resistance is not temperature sensitive, but RLC circuit resonance was environmentally sensitive to parasitic capacitance.
T.H. Chang of U Wisconsin, Madison showed a printing transfer method for fabricating flexible graphene transistors. The graphene was conventional CVD monolayer grown on copper film. Transfer is accomplished by proper sequencing of the surface energies of the device substrates and the transfer substrates so that the material you want moves when and where you want it to move. 140nm channel devices were fabricated with e-beam lithography.
Jean-Pierre Simonato of CEA Grenoble (France) presented a highly flexible transparent film heater based on metallic nanowires. The devices works on Joule heating, P=V2/R, of Ag nanowires. The device provides high heating rates and stable steady-state temperature control at operating voltages ≤12V. Sheet resistance is <20Ω/o up to 80% transmittance at 550nm. Unlike ITO, the Ag nanowire film is highly flexible, maintaining low resistance even during crinkling. The material set can be used to fabricate thermochromic displays. Heating and cooling rates are dominated by the substrate material, but good repeatability in thermal cycling was demonstrated with all substrates used. The group believes a reasonable trade-off can be achieved between transparency, conductivity and cost with the Ag nanowire system.
Junghyun Cho of SUNY Binghamton talked about the growth of nanostructured ceramic films from liquid solution. Their process strategy focuses on low temperature processing, mimicking biological processes where applicable. A variety of materials and applications were demonstrated, as shown in the table, with film morphology and as-deposited density depending on deposition parameters in solution. Activity is underway to extend the material/process technology to dye-sensitized solar cells in which the dye is incorporated into the ceramic film layer.
Toivo Kodas of Cabot Corp. gave an overview of functional nanomaterials technology at Cabot. His primary mission is to find problems that require particles as part of the solution, since the corporate banner is that they are the world’s largest ($3B) pure-play nanomaterials producer. Complex metal oxides made by spray pyrolysis are finding expanded use in security applications based on their unique spectral signatures, as they are extremely difficult to counterfeit. Custom coatings on gold nanoparticles exploit the surface enhanced Raman effect for security applications at extremely low reporter particle concentrations.
Also read Conference Report: TechConnect, Day 1