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Biomedical subjects

Rodney S Ruoff

Publications and source records attributed to Rodney S Ruoff.

8 recordsLinked to original sources
PubMed2006

Dielectrophoretic assembly of nanowires.

Nanowire (NW) assembly is currently of great interest, partly because NWs are considered as a fundamental component in the fabrication of a variety of devices. A powerful method has been developed to model the assembly of NWs. The three-dimensional dielectrophoretic (DEP) assembly of NWs across opposing electrodes is, for the first time, comprehensively studied using this new method. It is found that the DEP force reaches a maximum when the ratio of gap size to NW length is in the range 0.85-1.0. Both the magnitude and sign of the DEP torque on each NW varies with this ratio, and also with the orientation angle and the geometry and configuration of the electrode. The simulation of the dynamic assembly of individual and bundled NWs agrees with experiment. This method is of sufficient power that it will be of direct use in modeling DEP-based assembly and thus the manufacturing of nanoelectronic devices.

Journal Article↗
PubMed2006

Graphene-based composite materials.

Graphene sheets--one-atom-thick two-dimensional layers of sp2-bonded carbon--are predicted to have a range of unusual properties. Their thermal conductivity and mechanical stiffness may rival the remarkable in-plane values for graphite (approximately 3,000 W m(-1) K(-1) and 1,060 GPa, respectively); their fracture strength should be comparable to that of carbon nanotubes for similar types of defects; and recent studies have shown that individual graphene sheets have extraordinary electronic transport properties. One possible route to harnessing these properties for applications would be to incorporate graphene sheets in a composite material. The manufacturing of such composites requires not only that graphene sheets be produced on a sufficient scale but that they also be incorporated, and homogeneously distributed, into various matrices. Graphite, inexpensive and available in large quantity, unfortunately does not readily exfoliate to yield individual graphene sheets. Here we present a general approach for the preparation of graphene-polymer composites via complete exfoliation of graphite and molecular-level dispersion of individual, chemically modified graphene sheets within polymer hosts. A polystyrene-graphene composite formed by this route exhibits a percolation threshold of approximately 0.1 volume per cent for room-temperature electrical conductivity, the lowest reported value for any carbon-based composite except for those involving carbon nanotubes; at only 1 volume per cent, this composite has a conductivity of approximately 0.1 S m(-1), sufficient for many electrical applications. Our bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications.

Journal Article↗
PubMed2006

Mechanical properties of nanoparticle chain aggregates by combined AFM and SEM: isolated aggregates and networks.

Mechanical properties of nanoparticle chain aggregates (NCA) including tensile strength and Young's modulus were measured using an instrument incorporating an AFM tip under SEM imaging. The NCA were studied individually and as network films. Carbon NCA were made by laser ablation of graphite, and SnO2 NCA were made by oxidation of a tin compound. The films were deformable and showed elastic behavior. NCA serve as reinforcing fillers in rubber and films of SnO2 NCA for trace gas detection.

Carbon↗
PubMed2006

Fabrication of nanopores in a 100-nm thick Si3N4 membrane.

Textured alumina films have been used to fabricate nanoscale pores in Si3N4 membranes. A few nanometer-thick alumina layer was used as a masking material for nanopore fabrication, and the pattern was transferred into a 100-nm thick, 200 microm x 200 microm Si3N4 membrane by reactive ion etching (RIE). The nanopores were found to be concentrated in a approximately 150-microm diameter region at the center of the membrane.

Crystallization↗
PubMed2002

Crystalline boron nanowires.

Ideal nanowire interconnects for nanoelectronics will be refractory, covalently bonded, and highly conductive, irrespective of crystallographic orientation. Theoretical studies suggest that boron nanotubes should be stable and exhibit higher electrical conductivities than those of carbon nanotubes. We describe CVD growth of elemental boron nanowires, which are found to be dense nanowhiskers rather than nanotubes. Conductivity measurements establish that they are semiconducting, with electrical properties consistent with those of elemental boron. High conductivities should be achievable through doping.

Journal Article↗
PubMedDate not supplied

Effect of interlayer potential on mechanical deformation of multiwalled carbon nanotubes.

A study on the modeling and simulation of interlayer interaction in the multiwalled carbon nanotube (MWCNT) system is presented. We use an interlayer Morse potential previously developed from a local density approximation (LDA) treatment of a bilayer of graphite. We have fit this Morse potential to experimental high-pressure compressibility data for graphite and to a more extensive LDA equation of state (EOS) for graphite, and excellent agreement is observed. We employ this potential to treat the interlayer mechanics of MWCNTs, where the MWCNT is so highly deformed that interlayer separation well below approximately 0.34 nm, such as down to approximately 0.26 nm, is occurring. This, to our knowledge, is the first treatment that attempts to account for deformations that have the layers approaching each other at very high local (interlayer) stress levels. Since evaluating the interlayer potential for a large MWCNT system is computationally intensive, a continuum simulation approach is proposed that saves on computational time and thus on cost. Comparisons with experimental results of buckled and highly kinked MWCNTs are presented.

Computer Simulation↗