Not strictly open-hardware, but this paper by researchers at TU-Delft describes a new software package (written in Python) that provides low-level control of individual nozzles on many low-cost Epson office printers. This could provide a nice platform for hardware hacking on printed electronics, bio-printing, etc.
This is very cool! Perhaps this could be used to create an Open Hardware biomarker spotter like SPRi-Arrayer? http://www.horiba.com/scientific/products/surface-plasmon-resonance-imaging-spri/spri-platform/spotting-systems/details/spri-arrayer-78/