The present invention provides a microfluidic device for synthesizing an array of compounds and methods for using the same. In particular, the microfluidic device of the present invention comprises a solid support base, an elastomeric layer attached to the solid support, and a plurality of flow channels located within the interface between the solid support and the elastomeric layer. In addition, the solid support comprises a functional group for forming a bond with a reactive reagent. In some embodiments, the microfluidic device further comprises a second plurality of flow channels that intersect the first plurality of flow channels. A plurality of control channels are also present in the microfluidic devices of the present invention. The control channels can be actuated to regulate flow of fluids within the flow channel(s).