How To Make Electronic Displays With Mood Ring Ink
Soychemist writes "Print some thermochromic ink onto a sheet of paper, put metal heating elements on the other side, and you have a rudimentary color-changing display. Chemists in the Whitesides Group at Harvard think that the devices could be used to provide a simple readout from cheap medical tests and kits that check water for pollutants. In the past year, the same scientists have made a three-cent medical test and improvised a centrifuge with an egg beater. Their aim is to invent useful gizmos with everyday materials."
The summary links to Wired, which in turn links to the real article with the interesting details: http://www.rsc.org/delivery/_ArticleLinking/DisplayHTMLArticleforfree.cfm?JournalCode=LC&Year=2009&ManuscriptID=b905832j&Iss=Advance_Article