Elton Graugnard

Atomic Force Microscopy of DNA Self-Assembled Nanostructures for Device Applications

Hieu Bui et al. — Fri, 08 Oct 2010 09:16:15 PDT

DNA nanotechnology, which relies on Watson-Crick hybridization, is a versatile selfassembly process whereby a variety of complex nanostructures can be fabricated with sublithographic features.[1] Adopting this technology, 1012 identical devices can be synthesized to have hundreds of components with 1nm resolution. Example nanostructures include: 1) DNA motifs [2], 2) two-dimensional DNA crystals [3], and DNA origami [4]. Currently, this technology is being adopted towards electronic, optical, and opto-electronic devices.[5]

Kinetics of DNA and RNA Hybridization in Serum and Serum-SDS

Elton Graugnard et al. — Mon, 04 Oct 2010 14:21:23 PDT

Cancer is recognized as a serious health challenge both in the United States and throughout the world. While early detection and diagnosis of cancer leads to decreased mortality rates, current screening methods require significant time and costly equipment. Recently, increased levels of certain micro-ribonucleic acids (miRNAs) in the blood have been linked to the presence of cancer. While blood-based biomarkers have been used for years in cancer detection, studies analyzing trace amounts of miRNAs in blood and serum samples are just the beginning. Recent developments in deoxyribonucleic acid (DNA) nanotechnology and DNA computing have shown that it is possible to construct nucleic-acid-based chemical networks that accept miRNAs as inputs, perform Boolean logic functions on those inputs, and generate as an output a large number of DNA strands that can be readily detected. Since miRNAs occur in blood in low abundance, these networks would allow for amplification without using polymerase chain reaction. In this study, we report initial progress in the development of a DNA-based cross-catalytic network engineered to amplify specific cancer-related miRNAs. Subcomponents of the DNA network were tested individually, and their operation in serum, as well as a mixture of serum with sodium dodecyl sulfate, is demonstrated. Preliminary simulations of the full cross-catalytic network indicate successful operation.

Programmable Periodicity of Quantum Dot Arrays with DNA Origami Nanotubes

Hieu Bui et al. — Mon, 04 Oct 2010 14:21:23 PDT

To fabricate quantum dot arrays with programmable periodicity, functionalized DNA origami nanotubes were developed. Selected DNA staple strands were biotin-labeled to form periodic binding sites for streptavidin-conjugated quantum dots. Successful formation of arrays with periods of 43 and 71 nm demonstrates precise, programmable, large-scale nanoparticle patterning; however, limitations in array periodicity were also observed. Statistical analysis of AFM images revealed evidence for steric hindrance or site bridging that limited the minimum array periodicity.

Operation of a DNA-Based Autocatalytic Network in Serum

Elton Graugnard et al. — Tue, 07 Sep 2010 11:21:59 PDT

The potential for inferring the presence of cancer by the detection of miRNA in human blood has motivated research into the design and operation of DNA-based chemical amplifiers that can operate in bodily fluids. As a first step toward this goal, we have tested the operation of a DNA-based autocatalytic network in human serum and mouse serum. With the addition of sodium dodecyl sulfate to prevent degradation by nuclease activity, the network was found to operate successfully with both DNA and RNA catalysts.

Point-of-Contact, DNA-Based Amplifier for Detecting Cancer-Related Micro-RNA in Blood Serum

Elton Graugnard et al. — Tue, 07 Sep 2010 11:17:30 PDT

Photonic Band Tuning in 2D Photonic Crystals by Atomic Layer Deposition

Elton Graugnard et al. — Mon, 31 Aug 2009 19:25:57 PDT

Enhanced Tunable Bragg Diffraction in Large-Pore Inverse Opals Using Dual-Frequency Liquid Crystal

Elton Graugnard et al. — Mon, 31 Aug 2009 19:20:04 PDT

Large-pore TiO2 inverse opals were fabricated by atomic layer deposition in sintered polystyrene colloidal crystal templates and infiltrated with dual-frequency liquid crystal. The optical properties of the hybrid organic/inorganic structure were characterized by reflectance measurements of the Bragg peak, the position of which was tuned using a frequency dependent applied electric field. A 6 nm blueshift was observed for frequencies less than 13 kHz and a 13 nm redshift for frequencies above 13 kHz. These results demonstrate enhanced optical tunability in three-dimensional photonic crystals and are important for the development of active photonic devices.

Dispersion Control in Two-Dimensional Superlattice Photonic Crystal Slab Waveguides by Atomic Layer Deposition

D. P. Gaillot et al. — Mon, 31 Aug 2009 19:16:14 PDT

The frequency and dispersion of photonic bands in two-dimensional triangular-based superlattice photonic crystal Si slab waveguides were manipulated using atomic layer deposition. The samples were conformally coated with increasing thicknesses of TiO₂ and characterized by polarized angular-dependent reflectance measurements, which revealed shifts in the photonic band frequencies of 16% as well as continuous changes in band dispersion. The ability to tune toward zero group velocity by tuning band repulsion between same-polarization bands is demonstrated. Finite-difference time-domain calculations, combined with a dielectric weighting model, were used to assess the observed band and dispersion tuning.

Replicated Photonic Crystals by Atomic Layer Deposition Within Holographically Defined Polymer Templates

Elton Graugnard et al. — Mon, 31 Aug 2009 19:12:46 PDT

We report the replication of holographically defined photonic crystals using multistage atomic layer deposition. Low- and high-temperature atomic layer depositions were combined with selective etching to deposit and remove multiple conformal thin films within three-dimensional polymer templates. Using intermediate Al₂O₃ inverse replicas, temperature-sensitive SU-8 photonic crystal templates were faithfully replicated with TiO₂ and GaP, greatly increasing the dielectric contrasts of the photonic crystals. Optical measurements are in good agreement with the calculated band structures.