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Why your Kindle uses zero power to hold a page
💡 E-ink holds an image with no power because charged pigment particles physically stay where an electric field last pushed them — a property called bistability.
A phone screen has to redraw itself dozens of times a second just to keep showing a still image — that constant refreshing is why the battery drains as you read. An e-ink (electrophoretic) display works on a completely different principle: it only spends power when the picture changes, and draws nothing at all while you sit on a page. This property is called bistability — each pixel is stable in both its black and white states without any electricity holding it there.
The trick lives in millions of microscopic microcapsules, each about the width of a human hair. Inside every capsule is a clear fluid holding tiny pigment particles: white ones carrying a negative charge and black ones carrying a positive charge. When the display applies an electric field to a pixel, the particles physically migrate. Pull the white particles to the top surface and that pixel looks white; pull the black ones up and it looks black.
Because the particles simply stay put once moved, the page persists with the power off. Two more consequences fall out of this design: e-ink is reflective, bouncing ambient light like real paper instead of shining a backlight into your eyes, and it refreshes slowly — which is why video looks terrible on it but text is crisp and easy to read in bright sun.