VIF introduces local perturbation in a micrometric space. By applying a fast and small oscillation, a second-order streaming flow with a steady component emerges around the solid microstructures. Hayakawa et al. showed that a local swirling flow was induced around a cylindrical micropillar by applying rotational vibrations with amplitudes and frequencies of a few micrometers and several hundred hertz, respectively. This phenomenon was characterized in detail both experimentally and numerically. We utilize this phenomenon to agitate the sample fluid suspending the target NPs and capture microbeads with a specific affinity (Figure ). Initially, both particles are dispersed in microfluidic space. A local whirling flow around the pillars is induced when circular vibration was applied to the entire substrate, which stirs the NPs and capture beads. Through this process, the NPs are adsorbed onto the surface of the large-affinity capture microbeads. As the adsorption of the NPs proceeds, the capture beads form aggregates as they collide because the NPs serve as a binder. The concentration of NPs in the sample is estimated from the extent of aggregation of the capture beads.