Real-time gap impedance monitoring of dielectrophoretic assembly of multiwalled carbon nanotubes

We report on a real-time monitoring method for the assembly of a small number of multiwalled carbon nanotubes (MWNTs) by dielectrophoresis (DEP). A time-varying impedance model was developed to estimate the number of MWNTs which span an electrode gap indicated by the instantaneous decrease of gap impedance during DEP. Sudden decreases in gap impedance signals corresponding to tube deposition were measured. The impedance values agreed with the impedance model. Experiments confirmed that DEP assembly and measurement of gap impedance changes due to tube deposition can be accomplished with a single instrument, also providing a feedback signal for DEP process control