This paper presents a large-scale assembly method to deposit discrete multiwalled carbon nanotubes (MWCNTs) across gaps present in an electrode array. A parametric study showed that MWCNTs dispersed in a liquid could be deposited to individually span gaps by combining an alternating current (ac) and a direct current (dc) electric field in a given ratio; it was shown that the ac field (5 MHz) serves to selectively attract and the dc field to guide individual deposition. Repeated trials demonstrated accurate, discrete, and aligned deposition at room temperature with 90% yield over an electrode array having 100 gaps.

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This paper presents a new approach to gas sensing using a multi-walled carbon nanotube (MWCNT) subject to electrical breakdown. The electrical resistances of large-diameter MWCNTs were found to decrease in the presence of air after experiencing electrical breakdown, while pristine MWCNTs were not appreciably sensitive. The sensitivity could be controlled by manipulating the level of the electrical breakdown, and larger-diameter MWCNTs showed better sensitivity because they possess more damaged shells that can create more adsorption sites for oxygen molecules. It was suggested by theoretical calculations that the oxygen sensitivity might be associated with an oxidized junction that exists between the outer and inner shells of the nanotubes.

In this paper a computational technique is proposed to describe brittle fracture of highly porous random media. Geometrical heterogeneity in the ''open cell foam'' structure of the porous medium on a mesoscopic length scale ͑ϳ100 nm͒ is mapped directly onto a three-dimensional ͑3D͒ elastic network by using molecular dynamics techniques to generate starting configurations. The aspects in our description are that the elastic properties of an irregular 3D-network are described using not only a potential with a two-body term ͑change in bond length, or linear elastic tension͒ and a three-body term ͑change in bond angle, or bending͒, but also a four-body term ͑torsion͒. The equations for minimum energy are written and solved in matrix form. If the changes in bond lengths, bond-or torsion angles exceed pre-set threshold values, then the corresponding bonds are irreversibly removed from the network. Brittleness is mimicked by choosing small ͑ϳ1%͒ threshold values. The applied stress is increased until the network falls apart into two or more pieces. ͓S0163-1829͑96͒07146-9͔

Carbon nanotube (CNT) -extracted lithography (CEL) was developed to create high-quality nanoscale gaps defined by the size of CNTs. An individual multiwalled CNT (MWCNT) was deposited across electrodes by the composite electric field guided assembly method (CEGA) developed previously. After blanket deposition of a metal layer, the MWCNT was removed to obtain a nanoscale gap. The CEL can provide a technique for the mass fabrication of well-defined and precisely positioned nanosized gaps in a reproducible manner.