In the various immunoassays mentioned above, relatively large antigens, such as extracellular vesicles (EVs), viruses, and bacteria, are often important targets. Because these nanoparticles (NPs) have low diffusivity compared to small molecules, it is crucial to promote the complex formation of NPs and immobilized antibodies to realize rapid and sensitive detection. The use of microbeads offers the advantage of an increased area of the antibody-coated surface for adsorption. The adsorption of antigens is further facilitated by actively mixing the beads and sample fluid; however, conventional bulk mixing (e.g., rotational agitation) is inefficient at a scale of less than 100 µL.