Assay devices for combinatorial libraries

An apparatus suitable for conducting an assay for a combinatorial library, wherein the apparatus comprises:

• an assay device comprising at least 10,000 wells on a top surface of the assay device, wherein each of the at least 10,000 wells comprises a floor and side walls configured to retain one or more beads and one or more targets in an aqueous solution;
• and
• surface partitions separating a first well of the at least 10,000 wells from a second well of the at least 10,000 wells,
• wherein a distance along the top surface of the assay device from a nearest edge of the first well to a nearest edge of the second well is from about 10 microns (μm) to about 50 μm,
• wherein the second well is a nearest neighboring well to the first well,
• wherein at least a portion of each of the surface partitions comprises a hydrophobic layer,
• wherein the hydrophobic layer is configured to restrict spill-over of the aqueous solution from the first well to the second well,
• wherein the assay device has a top surface area, and a density of the at least 10,000 wells on the top surface area is at least 10 wells per square millimeter (mm2), and
• wherein each of the wells has a well diameter from about 30 μm to about 250 μm and a well depth from about 30 μm to about 400 μm.