Publications

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Even after decades of research, Li-ion cells still lack thermal stability. A number of approaches, including adding fire retardants or fluoro compounds to the electrolyte to mitigate fire, have been investigated. These additives improved the thermal stability of the cells (only marginally) but not enough for use in transportation applications. Recent investigations indicate that hydrofluoro-ethers are promising as nonflammable additives1. We describe here the results of our studies on electrolytes containing the hydrofluoro-ethers in cells fabricated at Sandia. In particular, we are investigating two solvents as nonflammable additives. These are: (1) 2-trifluoromethyl-3-methoxyperfluoropentane {l_brace}TMMP{r_brace} and (2) 2-trifluoro-2-fluoro-3-difluoropropoxy-3-difluoro-4-fluoro-5-trifluoropentane {l_brace}TPTP{r_brace}. These electrolytes not only have good thermal stability compared to the conventional electrolytes but respectable ionic conductivity. Sandia made 18650 cells successfully completed the formational cycle. The impedance behavior is typical of Li-ion cells.

Higher performance is the main driver in the integrated circuit (IC) market, but along with added function comes the cost of increased input/output connections and larger die sizes. Space saving approaches aimed at solving these challenges includes two technologies; 3D stacking (3D-ICs) and flip chip assemblies. Emerging ICs require sub-micron scale interconnects which include vias for 3D-ICs and bump bonds for flip chips. Photolithographic techniques are commonly used to prepare templates followed by metal vapor deposition to create flip chip bump bonds. Both the lithography step and the metal properties required for bump bonding contribute to limiting this approach to a minimum bump size of ∼10 μm. Here, we present a wet chemistry approach to fabricating uniform bump bonds of tunable size and height down to the nanoscale. Nanosphere lithography (NSL), a "soft" lithographic technique, is used to create a bump bond template or mask for nanoscale bumps. Electrochemical deposition is also used through photoresist templates to create uniform bump bonds across large area wafers or dies. This template approach affords bumps with tunable diameters from 100s of nanometers to microns (allowing for tunable interconnect pitch and via diameters) while the use of constant current electoplating gives uniform bump height over large areas (>1 cm2).

A molecular-scale interpretation of interfacial processes is often downplayed in the analysis of traditional water treatment methods. However, such an approach is critical for the development of enhanced performance in traditional desalination and water treatments. Water confined between surfaces, within channels, or in pores is ubiquitous in technology and nature. Its physical and chemical properties in such environments are unpredictably different from bulk water. As a result, advances in water desalination and purification methods may be accomplished through an improved analysis of water behavior in these challenging environments using state-of-the-art microscopy, spectroscopy, experimental, and computational methods.

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Microtubules and motor proteins are protein-based biological agents that work cooperatively to facilitate the organization and transport of nanomaterials within living organisms. This report describes the application of these biological agents as tools in a novel, interdisciplinary scheme for assembling integrated nanostructures. Specifically, selective chemistries were used to direct the favorable adsorption of active motor proteins onto lithographically-defined gold electrodes. Taking advantage of the specific affinity these motor proteins have for microtubules, the motor proteins were used to capture polymerized microtubules out of suspension to form dense patterns of microtubules and microtubule bridges between gold electrodes. These microtubules were then used as biofunctionalized templates to direct the organization of functionalized nanocargo including single-walled carbon nanotubes and gold nanoparticles. This biologically-mediated scheme for nanomaterials assembly has shown excellent promise as a foundation for developing new biohybrid approaches to nanoscale manufacturing.

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