The present invention provides microfluidic devices comprising elastomeric components and solid substrate component for attaching ligands and methods for conducting a variety of assays and high throughput screening. The elastomeric components comprise a plurality of first and second flow channels forming a plurality of intersecting areas, further capable of forming looped flow channels, and in fluid communication with the solid substrate surface, a plurality of control channels, a plurality of first and second control valves, and a plurality of loop forming control valves.