Inkjet printed active element on paper based on conductive and thermochromic materials

Inkjet printing is a suitable technology for fabricating rapidly and inexpensively electronic structures that contain layers made of different inks. It is easy to integrate several printheads together for printing multiple inks and these printheads don't require much space when compared to, for example, conventional printing units. Inkjet printing also has a very low material consumption which makes it possible to jet typically very expensive conductive inks. Therefore inkjet printing enables printing of inexpensive active electronic elements even on such low-cost products as packages or other paper-based products. VTT has developed and fabricated a game demonstrator that consists of six ink layers all inkjet printed. The layers were made from conductive, dielectric, thermochromic and regular inks printed on a paper substrate. The concept of the game was that a question and three alternatives for the correct answer were presented. When pressing any of the alternative answers, electrical contact between two ink layers triggered a colour-change reaction exposing whether the chosen answer was correct or incorrect. The reaction occurred in a couple of seconds. Although a working demonstrator was realized challenges still remain for the fabrication of an inexpensive, preferably inkjet printed, power source.