Abstract
Abstract Since their initial developments in the late 1980s, miniaturized sensors and actuators produced via microfabrication techniques have demonstrated compact footprint, high sensitivity, fast response time, and have thus garnered signification research attention. More recently, carbon nanotubes (CNTs) has been extensively explored for a variety of applications due to its unique electrical and exceptional mechanical properties, making it an excellent candidate as nano-scale sensors that promise to deliver even greater performances than micro-scale sensors. The assembly of CNTs into sensors, however, has been a challenge. Recently, dielectrophoresis (DEP), which utilizes micro-scale electrodes to generate non-uniform electric, has demonstrated its ability in manipulating micro-scale objects such as cells and even nano-scale objects such as CNTs. The DEP method, however, requires micro-scale metal electrodes that must be microfabricated in specialized facilities. Furthermore, DEP-based manipulation is restricted to the vicinity of the electrode. As an alternative to the traditional DEP method, optically-induced dielectrophoresis (ODEP) uses optical images illuminated on a photoconductive material (amorphous silicon in this study) as virtual electrodes to generate the DEP force, and therefore obviates microfabricated electrodes and is capable of particle manipulation without location restrictions. In this study, a new method that utilizes ODEP to manipulate CNTs, assemble CNT networks, and fabricate CNT-based nanosensors was demonstrated. Specifically, CNTs dissolved in ethanol were collected and concentrated by ODEP forces and aligned between a pair of metal electrodes that only served as electrical contacts for downstream sensor applications. After ethanol evaporated, CNTs became immobilized between the electrode pair. Because the resistivity of this CNTs assembly decreased as a function of increasing temperature, it was then applied as a temperature sensor and a hot-film anemometer, which could detect changes in wind speed. Offering efficient CNTs collection and ready-to-use sensor fabrication, this ODEP-based approach presents a promising method for the development the parallel assembly of CNT-based sensing applications. Keywords: Carbon nanotubes, dielectrophoresis, optically-induced dielectrophoresis, amorphous silicon, photoconductive material, hot-film anemometer