From bigclivedotcom.

Quite an odd and seemingly simple device. It consists of two layers of plastic, one black and one clear, and a film of liquid between them that shows a colour when drawn on with a stylus. When a button is pressed, a fairly high (more than 30V) DC voltage is applied across the film of liquid causing it to go transparent again.

This video was filmed in temporary accommodation while travelling with work.

Note that I described the conductive sheets as having a fairly low resistance, but in reality it is in the 100’s of thousands of ohms range as it appears to be just applying a capacitive electrical field across the film.

My guess is that the liquid has strands or platelets that are pressed flat by the stylus to show colour, but then re-align vertically when an electrical field is applied across them.

These toys are extraordinarily cheap. From as little as a few pounds. The two units that I took apart, both came from One Beyond in the UK, but despite looking identical, they contained different circuitry.

Per found a datasheet on the technology. It shows that it is a liquid crystal display with a spacer polymer to keep the panels apart.
https://datasheet.datasheetarchive.com/originals/crawler/kentdisplays.com/e76faa6baf82047d21381e2a8fd3cb28.pdf

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