This paper describes the assembly of 2 nm gold nanoparticles between micro-fabricated planar electrodes by using dielectrophoresis (DEP). The optimal conditions for effectively dieletrophoretic manipulation have been established through theoretical analysis and experimental validation. In the theoretical analysis, the effect of Brownian motion was taken into consideration, as well as the electrothermal flow and the AC electroosmosis flow. For effective manipulation of nanoparticles using DEP, proper high electric field strength is desired to give rise to dominate DEP effect, since the higher electric field strength increases the Joule heating and the lower strength reduces the DEP force. The current results indicate that the input voltage of 16Vp-p, 150 kHz leads to effective assembly of 2 nm gold nanoparticles. Our study proved that the DEP is capable of consistently assembling gold nanoparticles down to 2 nm in diameter with micro-fabricated electrodes, which was thought to be extremely difficult in the past.

Experimental results on varying particle size and dielectrophoretic (DEP) parameters, including voltage and frequency, are reported in this paper for investigating their effect on Au nano-particles Pearl Chain Formation (PCF). PCF was observed from 10kHz to 5MHz for 100nm gold Nano-particles (NPs), and 100kHz to 10MHz for 10nm gold NPs. Variations in formation rate were detected when the applied voltage and particle size varied. With higher voltage, pearl chain begins to form at higher rate and the formation time decreases. The optimum frequency of the gold NPs PCF shifts to higher frequency region when the particle size decreases. Theoretical analysis was carried out by applying the theories of DEP force and AC electrokinetics to explain the observations in the DEP frequency ranging from 10 Hz to 10MHz.