ERBB2 and breast cancer: Multiplexing capabilities, image acquisition, and sensitivityare simultaneously improved by trapping beads at defined positionsand utilizing fluorescently barcoded magnetic beads in combinationwith a single fluorescent reporter for the detection of all EV phenotypes.We study EVs secreted from two breast cancer cell lines, triple-negativeMDA-MB-231 and HER2-postive SkBr3.