Detection of nanoparticles in a minute sample using the vibration induced flow

We developed a microfluidic system for the detection of nanoparticles (NPs) with the vibration-induced flow (VIF), in which a mean flow is induced around a micro-pillar by applying the small periodical vibration. In this system, the presence of specific NPs in a sample fluid is evaluated by the extent of the aggregation of the affinity capture beads stirred by VIF. Here, we show that the amount of NPs in the sample correlates well with the average area of the capture bead aggregates formed within a short time (~10 min), which can be readily evaluated by the bright field microscope imaging. We also show that the extent of the aggregation depends on vibration parameters, and there is an optimal condition to detect NPs faster using VIF. Further, we succeeded in detecting the extracellular vesicles (EVs) using our system, for examination its applicability in real application. This method is simple and reproducible, so that it can be used as a versatile and reliable detection method of NPs in a minute sample.