Theory of simultaneous control of orientation and translational motion of nanorods using positive dielectrophoretic forces

The manipulation of individual submicron-sized objects has been the focus of significant efforts over the last few years. A method to arbitrarily move and orient a set of rod-shaped conductive particles in a region defined by a set of electrodes using positive dielectrophoretic forces is presented. While the orientation of each particle is directly specified through the angle of the local electric field, its position is indirectly controlled through the applied force. Each electrode is approximated as an unknown point charge and an induced dipole. Since each induced dipole results from the combination of all other sources, a set of linear constraints are derived to enforce the self-consistency of the system. Additionally, the force and orientation of each particle also form an additional set of linear constraints. This combined set of constraints is then solved numerically to yield the sources required to induce the desired orientation and motion of each particle. It is observed that the minimum number of electrodes that can be used to control a set of N particles is 4N+1. Numerical simulations demonstrate that the control of a single nanorod (diameter of 70 nm; length of 1.4μm) in the midst of a realistic electrode array can be accomplished under practical conditions. In addition, such control of orientation and motion can be achieved over an ample region in the vicinity of each rod

Tuning the resonant frequency of single-walled carbon nanotube bundle oscillators through electron-beam-induced cross-link formations

The authors investigate the effect of electron irradiation on the resonant frequency of single-walled carbon nanotube bundles. Electron beam irradiation was employed to induce the formation of intertube cross-linking. An increase in the resonant frequency was observed at low electron doses as the bending modulus was enhanced by cross-link formation. Higher doses induced amorphization and knock-on damage in the bundle, resulting in an overall reduction of the bending modulus. The effect of stiffness enhancement is more pronounced in larger diameter bundles due to the more compliant initial condition. At 45 nm diameter, an increase in bending modulus of 115% is observed

Electric Tweezers: Experimental Studies of Positive Dielectrophoresis-Based Positioning and Orientation of a Nanorod

The manipulation of individual micrometer sized objects has been the focus of significant research efforts over the last few years. A previously proposed method for the arbitrary manipulation of nanoparticles is experimentally demonstrated. This method employs dielectrophoretic forces for the planar control of the motion and orientation of such nanoparticles between a set of microfabricated electrodes. Each electrode is approximated as a set of sources, namely, an unknown point charge and induced dipole. Imposing constraints on the electric field at the location of the particle and requiring self-consistency uniquely determine the sources. They can then be subsequently used to determine the set of electrode voltages that creates an electric field that will produce the prescribed orientation and force on the particle. The drag coefficients of a nanorod are experimentally determined by sequentially applying a constant force both parallel and perpendicular to its axis and observing a resulting motion.With the drag coefficients in hand, the velocity rather than force can be prescribed, and the rod is directed to move accurately at oblique angles to its orientation. The rod is in a constant state of unstable equilibrium and requires negative feedback to maintain a fixed position. The automation of such feedback is demonstrated, allowing a controlled travel of the nanostructures over complex paths

Gas Sensing Properties of Single Conducting Polymer Nanowires and the Effect of Temperature

We measured the electronic properties and gas sensing responses of template-grown poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS)-based nanowires. The nanowires have a "striped" structure (gold-PEDOT/PSS-gold), typically 8um long (1um-6um-1um for each section, respectively) and 220 nm in diameter. Single-nanowire devices were contacted by pre-fabricated gold electrodes using dielectrophoretic assembly. A polymer conductivity of 11.5 +/- 0.7 S/cm and a contact resistance of 27.6 +/- 4 kOhm were inferred from measurements of nanowires of varying length and diameter. The nanowire sensors detect a variety of odors, with rapid response and recovery (seconds). The response (R-R0)/R0 varies as a power law with analyte concentration.Comment: 4 figures 8 pages, add 2 reference

Dielectrophoretically Assembled Polymer Nanowires for Gas Sensing

We measured the electronic properties and gas sensing response of nanowires containing segments of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) that were synthesized using anodic aluminum oxide (AAO) membranes. The nanowires have a "striped" structure of gold-PEDOT/PSS-gold and are typically 8 um long (1 um-6 um-1 um for each section, respectively) and 220 nm in diameter. Dielectrophoretic assembly was used to position single nanowires on pre-fabricated gold electrodes. A polymer conductivity of 11.5 +/- 0.7 S/cm and a contact resistance of 27.6 +/- 4 kOhm were inferred from resistance measurements of nanowires of varying length and diameter. When used as gas sensors, the wires showed a resistance change of 10.5%, 9%, and 4% at the saturation vapor pressure of acetone, methanol and ethanol, respectively. Sensor response and recovery were rapid (seconds) with excellent reproducibility in time and across devices. "Striped" template-grown nanowires are thus intriguing candidates for use in electronic nose vapor sensing systems.Comment: 18 pages 6 figure

Dielectrophoretic Assembly of Carbon Nanofiber Nanoelectromechanical Devices

We report a technique for the assembly of bottom-up nanomechanical devices. This technique employs the dielectrophoretic manipulation of nanostructures within a multiple layer lithography process. Mechanical resonators were specifically produced by assembling and clamping tubular carbon fibers onto prefabricated pads. Our preliminary results showed that an assembled cantilevered fiber with length L = 5 µm and width of W = 180 nm possessed a resonant frequency of f = 1.17 MHz. A shorter L = 3-µm-long singly clamped resonator of similar width showed a resonance of f = 3.12 MHz. This frequency range is in agreement with the low gigapascal bending moduli previously reported for carbon structures showing extensive volume defects. This technology would allow the integration of bottom-up nanostructures with other more established fabrication processes, thus allowing the deployment of engineered nanodevices in integrated systems

A suggested classification for two groups of Campylobacter myoviruses

Most Campylobacter bacteriophages isolated to date have long contractile tails and belong to the family Myoviridae. Based on their morphology, genome size and endonuclease restriction profile, Campylobacter phages were originally divided into three groups. The recent genome sequencing of seven virulent campylophages reveal further details of the relationships between these phages at the genome organization level. This article details the morphological and genomic features among the campylophages, investigates their taxonomic position, and proposes the creation of two new genera, the “Cp220likevirus” and “Cp8unalikevirus” within a proposed subfamily, the “Eucampyvirinae”.AMK would like to thank Andre Villegas for developing "extractUpStreamDNA". The authors are thankful to Denis Arutyunov and Jessica Sacher for helpful discussions and help with phage preparations, and to Cheryl Nargang for her help with nucleotide sequencing and analysis of gp047 homolog from phage F336. The bacteriophage receptor-binding protein studies were funded by an Alberta Innovates Scholar Award (CMS) and a Natural Sciences and Engineering Research Council of Canada Strategic Grant (CMS). RL and AMK are chair and vice chair, respectively, of the prokaryotic virus subcommittee of the ICTV (International Committee for Taxonomy of Viruses)

Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites

<p>This fileset contains all raw data and figures related to the article "Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites", submitted by Ramadan and Evoy to PLOS ONE, in March 2015</p