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The aim of this work was to study the formation process of dielectrophoretic (DEP) carbon nanotube fibers (CNT-fibers) and characterize the fiber properties relevant to their technological applications. The fiber diameter was shown to increase when applied voltage was increased (up to 350 V(pp)) and when retraction speed was decreased (down from 400 µm s(-1)) in accordance with theoretical expectations. This paper represents the first demonstration of the formation of thick DEP CNT-fibers (up to ∼ ∅0.4 mm). This is an intriguing result, as it expands the diversity of possible applications of the fibers and facilitates their characterization by analytical methods that require large quantities of the material. The performance of these thick fibers was as follows: a density of ∼ 0.35 g cm(-3), a tensile strength of ∼ 15 MPa, a Young's modulus of ∼ 1 GPa, and an electrical resistivity of ∼ 70 mΩ cm.

We report on a novel label-free biosensor for in situ measurements in liquid. It is comprised of a porous carbon nanotube (CNT) fibre attached to one prong of a quartz tuning fork (QTF) resonator. Only the protruding CNT fibre is immersed into a liquid, while the QTF is kept above the liquid to avoid short circuit of its electrodes. The low density and large surface area of the CNT fibre assure sufficient sensitivity without affecting the performance of the QTF significantly. Efficiency of the sensor was demonstrated experimentally by comparison of the adsorption rate of bovine serum albumin to the CNT fibre at two different pH values; differences in adsorption rates were clearly distinguishable.

Sol-gel derived silane hybrid films composing of (3-aminopropyl)trimethoxysilanetetramethoxysilane (APTMS-TMOS) have been shown to have properties that make the films suitable for DNA microarray applications. The ability of the films to bind DNA was studied using aminated 25-mer oligonucleotide DNA and 1,4-phenylenediisothiocyanate linker. The binding of DNA onto the films was shown to depend on films' composition, i.e. the binding rate decreased with the decrease of APTMS content in the film. The arrayed primer extension (APEX) analysis showed reversed tendency -fluorescence signals of bound probes increased with the decrease of APTMS content in the film. The background noise was low and the fluorescent probes were clearly outlined. The density of functional amino groups on the films was estimated by fluorescence spectroscopy.