The present invention provides an exchangeable, reagent pre-loaded sheets which can be temporarily applied to an electrode array on a digital microfluidic device (DMF). The substrate facilitates virtually un-limited re-use of the DMF devices avoiding cross-contamination on the electrode array itself, as well as enabling rapid exchange of pre-loaded reagents while bridging the world-to-chip interface of DMF devices. The present invention allows for the transformation of DMF into a versatile platform for lab-on-a-chip applications.