Abstract

Detection of nanoparticles (NPs) plays an important role in a wide variety of fields such as medical diagnostics and environmental monitoring. We have been developing a simple system for detecting NPs in small samples using vibration-induced flow (VIF), in which a mean flow is induced around a micropillar by applying small periodic vibrations. The system can evaluate the presence and concentration of specific NPs in a minute sample from the extent of aggregation of affinity capture beads agitated by VIF. This technique eliminates the use of fluorescent labeling or expensive image analysis equipment. In this study, we investigated the relationship between various flow patterns and capture bead aggregation. It was found that large vortex flows induced by circular and elliptical vibration produce large aggregations, whereas small vortex flows induced by rectilinear vibration produce a large number of small aggregations with relatively uniform sizes. This result indicates that the size of aggregations depends on the size of the vortices in the flow field and that can be readily controlled by the flow pattern tuned with vibration conditions.