an ultra - low voltage microfluidic device for manipulating droplets of liquid by inducing marangoni stress therein includes a plurality of smart - polymer electrodes having films of smart polymer exposed at their surfaces . the surface of the smart polymer becomes hydrophobic or hydrophilic in response to different electromagnetic potentials . the smart polymer is reversibly oxidized by applying an electrical potential such that the smart polymer acquires a positive electrical charge . the oxidized smart polymer is reduced by applying an electrical potential such that it loses its positive electrical charge . the smart polymer is doped with a chemical compound having a negatively - charged end and a long - chain hydrophobic tail . the smart polymer is a polypyrrole and the dopant is a dodecylbenzene sulfonate . the microfluidic device includes a plurality of individually - addressable control electrodes , each of which is electrically - connected with smart - polymer electrodes . droplets are transported , cut , or mixed by selectively applying electrical potential to individual electrodes .