Assay device and method for performing biological assays

An assay device comprising:

• a reaction chamber located in a microchannel;
• at least two sets of individually encoded functionalized microcarriers;
• at least one side of the microchannel being configured to allow for optical observation or identification of said microcarriers in the microchannel;
• each said microcarrier of one of the at least two sets having identical functionalization;
• a cross-section of the reaction chamber having a height and a width that is greater than the height;
• a cross-sectional width of each said microcarrier being less than half of the width of the cross-section of the reaction chamber such that at least two microcarriers arranged side by side without touching each other can pass each other in a longitudinal direction when they move at different speeds within the microchannel;
• and
• a movement restricting device structured and arranged to limit movement of the microcarriers.