Thermal characterization of micro/nanoscale conductive and non-conductive wires based on optical heating and electrical thermal sensing

Abstract

In this work, a technique based on optical heating and electrical thermal sensing (OHETS) is developed to characterize the thermophysical properties of one-dimensional micro/nanoscale conductive and non-conductive wires. In this method, the to-be-measured thin wire is suspended over two electrodes and is irradiated with a periodically modulated laser beam. The laser beam induces a periodical temperature variation in the wire/tube, which will lead to a periodical change in its electrical resistance. A dc current is applied to the sample, and the resulting periodical voltage variation over the wire is measured and used to extract the thermophysical properties of the wire/tube. A 25.4 µm thick platinum wire is used as the reference sample to verify this technique. Sound agreement is obtained between the measured thermal conductivity and the reference value. Applying the OHETS technique, the thermal diffusivity of conductive single-wall carbon nanotube (SWCNT) bundles and non-conductive human hair and cloth fibres are measured. For non-conductive wires, a thin (∼nm) metallic film is coated at the outside of the wire for electrical thermal sensing. The measured thermal diffusivities for three different SWCNT bundles are 2.98 × 10−5 m2 s−1, 4.41 × 10−5 m2 s−1 and 6.64 × 10−5 m2 s−1. These values are much less than the thermal diffusivity of graphite in the layer direction. For human hair and microscale cloth fibres, our experiments show that their thermal diffusivities are at the level of 10−6 m2 s−1.