Carbon Nanotube Chemical and Mechanical Sensors

A single-walled carbon nanotube (SW-CNT) is a nano scale tube formed by a cylindrical shell of single atomic layer of carbon atoms. Nanotubes have diameter of a few nm and length up to 100μm so that they form extremely thin wires. The atomic structure of SWCNT can be formed by wrapping a stripe of single atomic layer of graphite sheet along a certain direction, and this direction determines the diameter and chirality of the nanotubes. Experimental and theoretical studies have found that these nano-meter sized CNTs have novel electronic properties, which can be metallic or semiconducting, depending on their radius or chiralities [1-6]. Nanotubes can be used as electronic wire between two metal electrodes as shown in Fig. 1, and the conductance between the electrodes can be measured as a function of the gate bias voltage. Since the nanotube electronic property is a strong function of its atomic structure, mechanical deformations [7-8] or chemical doping can induce strong changes in conductance. Such changes can be easily detected by electron current signals, and these properties make CNTs extremely small sensors sensitive to their chemical and mechanical environments. In this paper, we present our theoretical and experimental studies on the subject of using SW-CNT as chemical and mechanical sensors.