Development of an automated microspotting system for rapid dielectrophoretic fabrication of bundled carbon nanotube sensors

An automated carbon nanotube (CNT) microspotting system was developed for rapid and batch assembly of bulk multiwalled carbon nanotubes (MWNTs)-based microelectromechanical system sensors. By using the dielectrophoretic and microspotting technique, MWNT bundles were successfully and repeatedly manipulated between an array of microfabricated electrodes. Preliminary experimental results showed that more than 75% of CNT functional devices can be assembled successfully using our technique, which is considered to be a good yield for nanodevice manufacturing. Besides, the devices were demonstrated to potentially serve as novel thermal sensors for temperature and fluid-flow measurements. This feasible batch manufacturable method will dramatically reduce production costs and production time of nanosensing devices and potentially enable fully automated assembly of CNT-based devices. Note to Practitioners - This paper was motivated by the problem of manipulate carbon naotube (CNT) across gold microelectrodes effectively and precisely. The purposed system potentially applies to other nano-sized particles that are neutral and with high polarizability. Existing methods of CNT assembly include guided CNT growth, external forces, polar molecular patterning, and atomic force microscopy (AFM) manipulation, which is time-consuming and unrealistic when considering batch production of CNT-based sensors. This paper reported a novel method to build CNT-based sensors across the microelectrodes by using our automated microspotting system. This system is integrated with a dielectrophoretic and microspotting technique. We first explained the dielectrophorectic effect on CNT - this method is very effective to manipulate CNT. Then, the microspotting technique was developed to spot a micron-sized CNT dilution droplet on the desired positions of a microchip substrate. Finally, dielectropheretic manipulation can be used to position CNT bundles across the microelectrodes. In this paper, we experimentally showed the difficulties to spot a micron-sized droplet, and the problems can be overcome by sharpening the spotting probe chemically and using the special spotting method. We then show the yield of CNT-based sensors fabricated by using this system is very promising. We also reported that the CNT-based sensors have low power consumption, and CNT can be used as the sensing element of the thermal sensor. The experimental results indicated this approach is feasible to develop batch manufacturing of nano devices.