Protocols are described for control of the electroosmotic flow in microfabricated channels in Vivak copolyester. Alkaline hydrolysis of surface ionizable groups alone or such hydrolysis in combination with dynamic coating with cetyltrimethylammonium bromide (CTAB) is shown to provide reproducible electroosmotic flows. Dynamic coating with CTAB can be used to eliminate electroosmosis or to reverse its direction, depending on the concentration employed.