Friction effect on the rotation of bichromal ball in a monolayer rotating ball display

A rotating ball display was tested with a thin monolayer sheet. An oil cavity was formed in the shape of a spheroid in a thin elastomer sheet. The rotation of a bichromal ball was investigated from the point of rotation time from one color to the other color. Bichromal balls were under friction during rotation. The friction caused an abnormal change in the rotation time. The rotation time of the elastomer sheet was compared with that of a microcup rotating ball display. The friction explained the difference of rotation time variation between the elastomer sheet display and the microcup display.