This paper presents an investigation on the humidity sensitivity of deposited multi-walled carbon nanotube (MWCNT) networks using ac dielectrophoresis (DEP) between interdigitated electrodes (IDEs). MWCNTs dispersed in ethanol were trapped and enriched between IDEs on a Si/SiO2 substrate under a positive DEP force. After the DEP process, the ethanol was evaporated and the MWCNT network on a substrate with IDEs was put into a furnace for repeated thermal annealing. It was found that the resistance stability of the network was effectively improved through thermal annealing. The humidity sensitivity was obtained by measuring the resistance of the MWCNT network with different relative humidity at room temperature. The experimental results show the resistance increases linearly with increasing the relative humidity from 25% to 95% RH with a sensitivity of 0.5%/%RH. The MWCNT networks have a reversible humidity sensing capacity with response time and recovery time of about 3 s and 25 s, respectively. The resistance is dependent on temperature with a negative coefficient of about −0.33%/K in a temperature range from 293 K to 393 K.
A structure similar to a field effect transistor with two isolated top electrodes comprising the source and drain and a lower substrate electrode as the gate was used for the dielectrophoresis-based assembly of zinc oxide nanowires. The results reveal that the assembly of nanowires is significantly affected by the gap distance between the two top electrodes as well as the magnitude and frequency of the applied electric field. Gate assisted assemblies using direct current and alternating current dielectrophoresis were also investigated and determined to improve the assembly effect of nanowires.
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