The book of the future may be made with radio paper and electronic ink.
(A) Radio paper has a coating of millions of tiny capsules; in each, there is a dark liquid and hundreds of white balls.
(B) Radio paper, oftentimes called e-paper, is a portable display medium that looks like paper but can be reused indefinitely.
(C) An electrical charge can make the white balls move to the top or bottom of the capsule to make the “ink” look white or black.
(D) Thus, the capsules could form letters on the page when they are charged in a pattern.