Nanospray Dielectrophoresis

Self-assembly of nanoparticles into microscale patterns by spray deposition and dielectrophoresis is investigated using microfabricated RF traps and nanospheres visualized using confocal fluorescence microscopy. Different combinations of spraying mode and trapping field lead to different results. Pneumatic spray and dielectrophoresis leads to sharply defined patterns at electrode edges, at the expense of particle clustering. In contrast, nanospray dielectrophoresis leads to improved particle dispersion due to charge repulsion, but suffers from dc focusing effects due to surface charges. Controlled switching between the different modes is demonstrated by manipulating the charge state of the nanospheres and the trapping potential.