Theoretical Model of Nanoparticle Detection Mechanism in Microchannel with Gating Probe Electrodes

In recent years, high-speed molecular detection technologies have attracted much attention and some important experimental results in this area have been reported. Tsutsui et al. successfully obtained electric signals of Au nanoparticles flowing in microchannels with gating nanoelectrodes [Tsutsui et al., Nano Lett., Vol. 9, No. 4 (2009), pp. 1659-1662]. The result of their study is expected to contribute to the fundamental development of high-speed DNA sequencers for the next generation. However, details of electro-fluid dynamics phenomena remain to be clarified. In the present study, a theoretical model is developed to explain the mechanism of the detection of charged metallic particles using gating nanoelectrodes, focusing on electric transient responses observed experimentally. The behavior of charges in the experimental system is discussed theoretically, and the resistance, capacitance, and time constant produced by the interaction between a metallic nanoparticle and the gating electrode are quantitatively evaluated. The theoretical result is in reasonable agreement with the experimental data obtained using Au nanoparticles. Thus, the present method is applicable to the study of more complex systems in which molecular fluid dynamics affects electric response.