Vienna University of Technology unveiled their prototype for the world's smallest 3D printer in May this year developed by Klaus Stadlmann and Markus Hatzenbichler. Klaus recently presented the micro-printer at TEDx Vienna, on crutches..
What these 2 students did was to automate a fairly simple process developed by Professor Nicholas Fang at the Nano-CEMMS center at the University of Illinois.
Using liquid-like monomer (see the short videos on the link below) and a pico DLP projector to project slices of a model one after another manually on top the liquid while lowering the base-platform by a fraction of a mm into the liquid - thus creating layer after layer until the model is finished.
These guys used a pico DLP projector and an arduino with a mini stepper motor to automate the process. Great job!
The liquid cost around $200 a litter and at least in my country requires a permit from the health officials to research with it.. (manufactured by Sigma-Ulrich and they are VERY strict about it)
Taking the development further by testing different "user-friendly" chemicals will pave the way to commercialize it, otherwise it will be for a specific market which isn't us.. designers/modelers... home users.
Still waiting for parts-order i made to take a shot at this