Apparatus and methods for manipulating microdroplets

A method of manipulating adherent cells contained in microdroplets on a surface of a microfluidic chip comprising an oEWOD active stack, the method comprising:

• positioning first microdroplets on one or more target regions of the surface, the first microdroplets containing adherent cells;
• allowing the cells from the first microdroplets to adhere to the target regions;
• introducing second microdroplets to the target regions, the second microdroplets containing a release reagent;
• and
• merging the first microdroplets with the second microdroplets, such that the release reagent causes the cells from the first microdroplets to detach from the target regions.