A new carbon nanotube-based hot-film sensor assembled by optically-induced dielectrophoresis

Miniaturized sensors have been demonstrated by micromachining technology since late 1980s. Recently, carbon-nanotubes (CNTs) have been extensively explored for a variety of applications since they have unique electrical and exceptional mechanical properties, which may be excellent candidate for nano-sensors. Conductors or semiconductors can be formed with different length and diameters of CNT, multiwalled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCMTs). Optically-induced dielectrophoresis (ODEP) technique has been demonstrated to manipulate microparticles by illuminating optical patterns on a photoconductive material. The ODEP chip was formed with indium-tin-oxide (ITO) and photoconductive amorphous silicon (a-Si). When the light was illuminated on a-Si, it could produce non-uniform electric field and generate ODEP force. In this study, CNTs were collected between two gold electrodes by ODEP force. The pre-assembled CNTs line was further immobilized by illuminated ultraviolet light. Then, the cured polymer was ashed by the oxygen plasma. After aligning CNTs between Au electrodes, the CNTs line can be used for sensing air flow velocities while operated at a constant-current mode. A CNT-based hot-film sensor was therefore successfully demonstrated in this study. This technique can be easily extended for mass-production of CNT-based hot-film sensorsby using the capability of ODEP platform.