Abstracts

Colloidal Interactions, Dynamics, and Assembly on Energy Landscapes

Dr. Michael A. Bevan
Johns Hopkins University

The ability of nano- and micro- scale components to autonomously and reversibly assemble on energetic templates is broadly considered as an enabling process to numerous emerging technologies.  As a result, there is strong interest in understanding how thermal motion, particle interactions, energetic templates, and external fields can be optimally coupled in assembly processes to elicit desired material and device responses.  We approach this problem by directly relating equilibrium and dynamic colloidal microstructures to the combined effects of many-body interactions and kT-scale energy landscapes due to physically and chemically patterned surfaces.  Colloidal trajectories are measured in 3D real space with nanometer resolution using integrated evanescent wave, video, and confocal microscopy methods.  Equilibrium structures are connected to energy landscapes via statistical mechanical analyses, and colloidal dynamics are interpreted using theories for self-diffusion and Stokesian dynamics simulations.  Findings from this work provide essential information to formally engineer (i.e. design, control, optimize) self- and directed- colloidal assembly processes on energetic patterns.  Approaches developed in this work are currently being extended to investigate biomolecular systems.

Measuring Carbon Nanotubes

Dr. Jeffrey Fagan
NIST

Single-wall carbon nanotubes (SWCNTs) are among the most exciting nanomaterials developed to date, and have the potential to enable next generations of technologies such as of transistors, photovoltaics, transparent thin film conductors, sensors, and fuel cell electrodes.  In practice however, the inhomogeneous mixture of nanotubes, catalyst, and impurities in raw soot, and the bundled morphology of SWCNTs after synthesis, have substantially hindered achievement of the properties necessary for these applications.  At the National Institute of Standards and Technology (NIST), we have applied a separation and characterization strategy using liquid phase methods developed for polymers, colloids, and biomolecules to improve the measurement science of carbon nanotubes.  The results of these efforts, their effects on the observed properties of the purified SWCNTs, and their incorporation into documentary standards and reference materials will be presented.

Bridging the Valley of Death: Resources for Accelerated Clinical Translation of Nanomedicine for Cancer

Dr. Anil K. Patri
Nanotechnology Characterization Laboratory

Promising drug discoveries in basic research often do not end up in clinic due to lack of adequate resources in advanced pre-clinical assessment. This ‘valley of death’ is often a huge stumbling block and cost-prohibitive in drug development. For Nanomedicine, the progress of such therapies from early research stage through pre-clinical development requires a collaborative effort with multi-disciplinary teams that leverages resources from government, industry, and academia.   Realizing the potential of Nanotechnology based technologies for cancer treatment and diagnosis, the National Cancer Institute (NCI) has established the Nanotechnology Characterization Laboratory to accelerate the clinical translation of urgently needed cancer therapies. A multi-agency collaborative effort between the NCI, the National Institute of Standards and Technology (NIST) and the U.S. Food and Drug Administration (FDA), the NCL is a unique resource that provides advice and support through testing. Once accepted, beyond a proof-of-principle stage development, NCL conducts thorough preclinical testing through standardized analytical cascade that includes nanomaterial physico-chemical evaluation, in vitro biological and biocompatibility testing, and their in vivo safety and efficacy assessment in animal models.  NCL has conducted preclinical assessment of various classes of material including polymers, dendrimers, nanoemulsions, liposomes, colloidal particles, fullerenes, quantum dots, and core-shell nanostructures.  Some of these concepts have advanced to the clinic and others are in the advanced pre-clinical development.

This presentation will cover the preclinical characterization resources and collaborative opportunities available to researchers for advancing their concepts to clinic.  Data pertaining to the structure-activity relationship studies on nanomaterial and trends in biocompatibility will be presented.

Applications of Nanocrystalline Diamond Films

Dr. James E. Butler
Naval Research Laboratory

The nucleation and growth of nanocrystalline diamond films by chemical vapor deposition will be presented.  Nanocrystalline diamond films have distinct properties from ultrananocrystalline diamond films reported by other groups.  Nanodiamond films grown by chemical vapor deposition exhibit a number of remarkable properties desirable for MEMS and NEMS.  These include high Young’s Modulus, thermal diffusivity, dielectric breakdown strength, mass density, secondary electron yields, fracture toughness, optical transparency, corrosion resistance, biological stability, and more.  The nucleation, growth, and doping of these films on diverse substrate materials, including Si, poly Si, SiO2, SixNy, SiC, GaN, and various metals, will be described along with various methods of processing into structures and devices. 

Overview of Nanomaterials Research at the DARPA Defense Sciences Office

Dr. Viktoria Greanya
DARPA

The Defense Sciences Office at DARPA funds a variety of nanomaterial related efforts.  This research provides a pathway to significant improvement in functional material properties. This talk will provide a brief overview of some of the exciting programs at DARPA DSO.

Building Tissues from the Nanoscale and Beyond

Dr. Jennifer Elisseeff
Johns Hopkins University

Nanoscience and engineering play an important role in materials science and regenerative medicine.  Both synthetic and biologically-derived biomaterials have a nanostructure that can be engineered and optimized to guide biological processes and ultimately tissue repair for reconstruction of traumatic injuries.  Biomaterial scaffolds have been generated in the form of gels, sponges, membranes and fibers depending on tissue target and clinical application.  In particular, a biomimetic extracellular matrix has been generated that incorporates nanofibers embedded in a hydrogel.  These scaffolds have been implemented for in vitro culture for fundamental studies of normal and diseased tissue development.  Enabling technologies have been developed to promote clinical translation of these technologies in the fields of orthopedics, ophthalmology, and plastic surgery.

Fluorescence Enhancement by Surface Plasmon Polaritons

Dr. Christopher C. Davis
University of Maryland

Surface plasmon polaritons (SPPs) can be excited on nanostructured surfaces from free space. The strong local surface electric fields that result can enhance fluorescence from various kinds of fluorophores, including quantum dots, placed on the surface.  The relationship between observed enhancement and geometrical factors of the surface structure has been used to explore the behavior of fluorophores on different substrates.  Imaging using standard fluorescence optical microscopy clearly demonstrates a strong dependence of fluorescence enhancement on fundamental parameters for periodic surface structures.  Two-dimensional cloaking techniques open the possibility of spatial control of fluorescence produced by SPPs.

References

Yu-Ju Hung, Igor I. Smolyaninov, and Christopher C. Davis, “Fluorescence enhancement by surface gratings,” Optics Express,  Vol. 14, No. 22, 30 October 2006, pp 10825-10830

Ehren Hwang, Igor I. Smolyaninov, and Christopher C. Davis,  “Surface plasmon polariton enhanced fluorescence from quantum dots on nanostructured metal surfaces. NanoLetters, 2010, 10 (3), pp 813–820

I. I. Smolyaninov, Y. J. Hung, and C. C. Davis, “Two-dimensional metamaterial structure exhibiting reduced visibility at 500 nm,” Optics. Letters. 33, 1342-1344 (2008)

Bi conduits and the road to spin-based electronics

Dr. Tito Huber
Howard University

Spin orbit (SO) coupling is attracting interest because it offers a path to sort electrons by their spin, a key feature of spin-based electronics. Despite its prevalence in solid state systems, in the bulk one usually finds time-reversal symmetry, which combined with space-inversion symmetry, makes every band spin-degenerate. At the crystal surface, on the other hand, the degeneracy will be lifted due to the loss of the space-inversion symmetry; each of the SO-split bands will carry only one electron. The effect gives rise to a new set of spin-split bands, surface states, that have been observed directly using angle resolved photoemission spectroscopy in many materials including Bi and BiTe. However the electronic transport by the surface states is not well characterized. We have studied 18-200 nm diameter bismuth nanowires, via magnetoresistance and thermopower down to low temperatures and for fields up to 14T and observed the electronic transport associated with the surface states. For single-crystal 50-nm nanowires, the bulk-like carriers are completely absent; the semimetal-to-semiconductor transition is a factor and possibly also the triviality-non-triviality character of the surface states as discussed in the theory of topological insulators. We observe that transport periodic in magnetic field where the modulation corresponds to the cyclic Aharonov-Bohm phase including a Berry phase. The nanotube behavior is consistent with the surface carriers undergoing quantum interference in the periphery of the wire; each oscillation corresponding to the filling of one-dimensional conduction channels along the nanowire axis; the Berry phase corresponds to the spin-orbit internal field. We will discuss the spin texture that is inferred from the measurements and our view of the outlook of spin-based electronics based on Bi conduits.