Arrayed Electrostatic Scratch Drive Actuators: Toward Visible Effects up to the Human Scale

This paper investigates millimeter scale electrostatic motors designed through a new "bottom-up design approach." Active polysilicon sheets involving thousands of elementary scratch drive actuators are analyzed, according to the driving force superposition capabilities of distributed electrostatic actuators. Driving forces as high as 1 00,000 pIN are reported in this paper, using 6 mm ² polysilicon sheets that integrate up to 1430 elementary scratch drive actuators. The mechanical power transmission from the sheet to the external load is also investigated. Because of structural height limitations, active polysilicon sheets do not allow significant driving forces to be transmitted to the external world. Therefore, original architectures, such as tubular electrostatic motors, are proposed using the insertion of a flexible polysilicon stator within the gap of a macroscopic cylindrical joint. An original self-assembling method is used in order to develop a first generation of millimeter scale electrostatic actuators. Expected performances that are evaluated from the in situ sheet characterization (i.e., from characterization onto the silicon wafer) point out the relevance of the bottom-up design methodology proposed in this paper. For the first time, visible effects up to the human scale are conceivable from silicon-based electrostatic motors that will allow innumerable actuation applications to be performed in the near future.