The central type shutter mechanism comprises main parts including a high-speed motor, a one-circle clutch, a driving wheel system, two blades and the like.

中心式快门机构包括高速电机、一周离合器、传动轮系、两片叶片等主要部件。

youdao

Obviously an eyelid-like shutter mechanism would be too large and complicated for something as small as a print head, so an electrical field is applied instead to keep the film spread thin.

ENGADGET: Alt-week 7.28.12: social mathematics, Pluto's moons and humans-on-a-chip