C. Jeffrey Brinker

Free-Meniscus Coating Processes

When faced with depositing a liquid film on a surface, laboratory scientists usually rely on free coating by withdrawal or drainage, or so-called free-meniscus coating. Simplistic and inexpensive, these techniques abound in the research and development of materials that can be deposited in the liquid state. What has come to be known as dip coating (Deryagin and Levi 1964; Ruschak 1976; Scriven 1988), viscous lifting (Van Rossum 1958), or drag-out (Landau and Levich 1942) begins with immersing a substrate in a vessel filled with liquid. Withdrawal of the substrate from the liquid, if managed properly, can result in a thin coherent liquid film, as shown in Fig. 13.1b. Alternatively, the liquid in the vessel can be drained around the substrate. This technique is often referred to as coating-by-drainage (Jeffreys 1930; Van Rossum 1958; Groenveld 1971) and is diagrammed in Fig. 13.1c. Recourse is sometimes taken from dip coating to coating-by-drainage when limited vertical space prevents substrate withdrawal (cf. Ashley and Reed 1984) or when coating small, short substrates to avoid the local thickening obtained when the trailing edge is withdrawn (Schroeder 1969). Although most often dip coating is operated as a batch process, it can be made continuous (Fig. 13.1d) when the substrate is a long, flexible sheet or filament (Deryagin and Levi 1964; Scriven 1988); however, sustaining a continuous coating process requires the addition of make-up liquid to the vessel. In any case, the physics of batch dip coating, continuous dip coating, and coating-by-drainage are essentially the same, differing only in the frame of reference in which the flat part of the meniscus is stationary.

Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.

The United States is now re-assessing its nuclear waste disposal policy and re-evaluating the option of moving away from the current once-through open fuel cycle to a closed fuel cycle. In a closed fuel cycle, used fuels will be reprocessed and useful components such as uranium or transuranics will be recovered for reuse. During this process, a variety of waste streams will be generated. Immobilizing these waste streams into appropriate waste forms for either interim storage or long-term disposal is technically challenging. Highly volatile or soluble radionuclides such as iodine ({sup 129}I) and technetium ({sup 99}Tc) are particularly problematic, because both have long half-lives and can exist as gaseous or anionic species that are highly soluble and poorly sorbed by natural materials. Under the support of Sandia National Laboratories (SNL) Laboratory-Directed Research & Development (LDRD), we have developed a suite of inorganic nanocomposite materials (SNL-NCP) that can effectively entrap various radionuclides, especially for {sup 129}I and {sup 99}Tc. In particular, these materials have high sorption capabilities for iodine gas. After the sorption of radionuclides, these materials can be directly converted into nanostructured waste forms. This new generation of waste forms incorporates radionuclides as nano-scale inclusions in a host matrix and thus effectively relaxes the constraint of crystal structure on waste loadings. Therefore, the new waste forms have an unprecedented flexibility to accommodate a wide range of radionuclides with high waste loadings and low leaching rates. Specifically, we have developed a general route for synthesizing nanoporous metal oxides from inexpensive inorganic precursors. More than 300 materials have been synthesized and characterized with x-ray diffraction (XRD), BET surface area measurements, and transmission electron microscope (TEM). The sorption capabilities of the synthesized materials have been quantified by using stable isotopes I and Re as analogs to {sup 129}I and {sup 99}Tc. The results have confirmed our original finding that nanoporous Al oxide and its derivatives have high I sorption capabilities due to the combined effects of surface chemistry and nanopore confinement. We have developed a suite of techniques for the fixation of radionuclides in metal oxide nanopores. The key to this fixation is to chemically convert a target radionuclide into a less volatile or soluble form. We have developed a technique to convert a radionuclide-loaded nanoporous material into a durable glass-ceramic waste form through calcination. We have shown that mixing a radionuclide-loaded getter material with a Na-silicate solution can effectively seal the nanopores in the material, thus enhancing radionuclide retention during waste form formation. Our leaching tests have demonstrated the existence of an optimal vitrification temperature for the enhancement of waste form durability. Our work also indicates that silver may not be needed for I immobilization and encapsulation.

Nature versus nurture in cellular behavior and disease.

This project pursued two complementary, interrelated goals: 1) the incorporation of individual or groups of bacterial, fungal, or mammalian cells within novel three-dimensional (3D) cell-built or lithographically defined matrices that provide an engineered chemical and physical background to inform cells and direct their behavior; and 2) the development of two classes of targeted nanoparticle delivery platforms, protocells (porous nanoparticle supported lipid bilayers) and virus-like particles (VLPs), which could be selected against dormant/drug resistant/metastatic cells and selectively deliver multicomponent cargos (cocktails) to this recalcitrant population. This project provided a unique means to understand environmental influences on cellular behavior, in particular, dormancy, drug resistance, metastasis and

Identification and display of CRLF2 ligands for targeted nanoparticle delivery to acute lymphoblastic leukemia.

This is the final report for the Sandia Excellence in Engineering Fellowship awarded through the School of Engineering at the University of New Mexico for the 2011-2012 academic year. Acute Lymphoblastic Leukemia (ALL) is the leading cause of cancer death in children. Almost 80% of the children diagnosed with ALL survive, but in order to reach that point, they must undergo intense regimens of systemic chemotherapy with shortand longterm side effects. Moreover, a significant percentage of cases (~30%) show high-risk features that result in relapse or failure to respond to treatment and account for most deaths. The long term goal of this project is to produce nanoparticles based on virus-like particles (VLPs) of the bacteriophage MS2 that specifically target ALL cells for delivery of cytotoxins. By taking advantage of the overexpression in high-risk pediatric ALL of the thymic stromal lymphopoietin (TSLP) receptor, CRLF2, it is possible to identify a peptide ligands specific for the receptor. We recently developed a peptide display and affinity selection system based on MS2 VLPs, thus integrating the targeting ligand identification and drug delivery functions into a single particle. This report summarizes work accomplished toward this goal.

Polymer/inorganic superhydrophobic surfaces.

We have designed and built electrostatically actuated microvalves compatible with integration into a PDMS based microfluidic system. The key innovation for electrostatic actuation was the incorporation of carbon nanotubes into the PDMS valve membrane, allowing for electrostatic charging of the PDMS layer and subsequent discharging, while still allowing for significant distention of the valveseat for low voltage control of the system. Nanoparticles were applied to semi-cured PDMS using a stamp transfer method, and then cured fully to make the valve seats. DC actuation in air of these valves yielded operational voltages as low as 15V, by using a supporting structure above the valve seat that allowed sufficient restoring forces to be applied while not enhancing actuation forces to raise the valve actuation potential. Both actuate to open and actuate to close valves have been demonstrated, and integrated into a microfluidic platform, and demonstrated fluidic control using electrostatic valves.

Exploiting interfacial water properties for desalination and purification applications.

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.

Nanoporous films for epitaxial growth of single crystal semiconductor materials : final LDRD report.

This senior council Tier 1 LDRD was focused on exploring the use of porous growth masks as a method for defect reduction during heteroepitaxial crystal growth. Initially our goal was to investigate porous silica as a growth mask, however, we expanded the scope of the research to include several other porous growth masks on various size scales, including mesoporous carbon, photolithographically patterned SU-8 and carbonized SU-8 structures. Use of photolithographically defined growth templates represents a new direction, unique in the extensive literature of patterned epitaxial growth, and presents the possibility of providing a single step growth mask. Additional research included investigation of pore viability via electrochemical deposition into high aspect ratio photoresist. This project was a small footprint research effort which, nonetheless, produced significant progress towards both the stated goal as well as unanticipated research directions.

Biocompatible self-assembly of nano-materials for Bio-MEMS and insect reconnaissance.

This report summarizes the development of new biocompatible self-assembly procedures enabling the immobilization of genetically engineered cells in a compact, self-sustaining, remotely addressable sensor platform. We used evaporation induced self-assembly (EISA) to immobilize cells within periodic silica nanostructures, characterized by unimodal pore sizes and pore connectivity, that can be patterned using ink-jet printing or photo patterning. We constructed cell lines for the expression of fluorescent proteins and induced reporter protein expression in immobilized cells. We investigated the role of the abiotic/biotic interface during cell-mediated self-assembly of synthetic materials.

Nanostructured Materials Integrated in Microfabricated Optical Devices

This project combined nanocomposite materials with microfabricated optical device structures for the development of microsensor arrays. For the nanocomposite materials we have designed, developed, and characterized self-assembling, organic/inorganic hybrid optical sensor materials that offer highly selective, sensitive, and reversible sensing capability with unique hierarchical nanoarchitecture. Lipid bilayers and micellar polydiacetylene provided selective optical response towards metal ions (Pb(II), Hg(II)), a lectin protein (Concanavalin A), temperature, and organic solvent vapor. These materials formed as composites in silica sol-gels to impart physical protection of the self-assembled structures, provide a means for thin film surface coatings, and allow facile transport of analytes. The microoptical devices were designed and prepared with two- and four-level diffraction gratings coupled with conformal gold coatings on fused silica. The structure created a number of light reflections that illuminated multiple spots along the silica surface. These points of illumination would act as the excitation light for the fluorescence response of the sensor materials. Finally, we demonstrate an integrated device using the two-level diffraction grating coupled with the polydiacetylene/silica material.

Protective coatings for concrete

The new two-layer protective coating developed for monuments constructed of limestone or marble was applied to highway cement and to tobermorite, a component of cement, and tested in batch dissolution tests. The goal was to determine the suitability of the protective coating in retarding the weathering rate of concrete construction. The two-layer coating consists of an inner layer of aminoethylaminopropylsilane (AEAPS) applied as a 25% solution in methanol and an outer layer of A2** sol-gel. In previous work, this product when applied to calcite powders, had resulted in a lowering of the rate of dissolution by a factor of ten and was shown through molecular modeling to bind strongly to the calcite surface, but not too strongly so as to accelerate dissolution. Batch dissolution tests at 22 C of coated and uncoated tobermorite (1.1 nm phase) and powdered cement from Gibson Blvd. in Albuquerque indicated that the coating exhibits some protective behavior, at least on short time scales. However, the data suggest that the outer layer of sol-gel dissolves in the high-pH environment of the closed system of cement plus water. Calculated binding configuration and energy of AEAPS to the tobermorite surface suggests that AEAPS is well-suited as the inner layer binder for protecting tobermorite.