Butterflies get a life by colour-changing inks

It's like finger painting, only without the messy paint. Impressions of a sensor on paper printed with color shifting ink could bring more interactivity to books and wallpaper.

Adding rigid wires and LEDs for a sheet of paper is a way to create color-changing paper. But Kohei Tsuji and Akira Wakita, both at Keio University in Japan, wanted to create the same effect without the paper softness and flexibility.

The color-shifting ink printed on one side of a sheet of paper and painted pasta to perform an electrical circuit to the other side. Touching the paper activates a brass pressure sensor attached to the back of the paper. This sends electricity through the painted silver wires, which are made of carbon paste electrodes heats. Heat radiates through the paper for color-changing ink on top.


This ink is a liquid crystal and the molecules to organize themselves in distorted helices when heated. The natural structure helices interact with light and reflects only a few wavelengths. The material changes color from red to blue to green when it warms up because the liquid crystal varies with temperature.

In a demonstration, Wakita Tsuji and pressed a butterfly with color shifting ink in the wings. By pressing the middle of the butterfly causes waves of color to spread its wings.

Wakita and Tsuji also an opaque ink that is transparent when heated. They created an interactive star atlas that shows the shape of the constellations and reveal their history with just one touch. Schedules printed in Rainbow ink an overview of the stars in the constellation. Opaque ink deals with both the words and a picture that describes the constellation.

The opaque ink seems to dissolve when the paper is touched, revealing the rainbow ink on top of an image of the object in the constellation and a text description of hi

The paper works will be shown at Siggraph Asia in December.

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