Alessandro Volpato, Biologist and inventor from Berlin, developed a process to etch ITO coated foil into completely transparent digital microfluidic devices. By applying a photo-resist, then exposing and developing  it like PCBs and finally etching with hydrochloric acid he can print any structure down to 0.1 mm into the conductive ITO coating. A sample I got for my birthday I connected to the OpenDrop and gave it a try. And it works great.

Applications such as use in mobile phone screen are possible ( http://bioengineering.illinois.edu/news/article/23435 ).

The etched ITO foil device. Contacted with cooper tape and silver lacquer.

OpenDrop, with spring contact board to connect external device.

ITO foil covered with parafilm and silicon oil to make it hydrophobic. Droplet from water with blue ink.