Electronic ink sign. Close-up of a letter in a sign printed with electronic ink. Materials coated in this ink can have text downloaded onto them electronically. The digital nature of the ink allows the text to be changed so a book, for example, can hold many titles. The ink consists of tiny transparent spheres containing microscopic white balls and a blue dye. When an electric current is applied, the balls, or microcapsules, rise up through the blue dye and become visible, or sink. By controlling where they rise and where they sink, a message can be formed. The ink was developed by Joseph Jacobson at MIT, USA. The sign was made by E Ink, a company Jacobson co-founded.