This latest instance apparently began when Hebrew University professor Shlomo Magdassi was working to develop a touchscreen using silver nanoparticles but ran into trouble making the screen conductive while still remaining transparent.

ENGADGET: Coffee-like stains inspire new type of touchscreen

Xerox is experimenting with its own conductive inks for making electronic paper and circuitry for flat screen monitors and billboards.

FORBES: Touchy Circuits