TABLE OF CONTENTS The micro-actuators described so far have been easily categorized by their topology: parallel plates capacitance, comb-drive actuator, torsion mode mirror and finally the rotating micro-motor. Nevertheless, the flexibility of microsystem technologies combined with the ease of production of electrostatic actuation have led to actuation devices or systems that cleverly combine the above mentioned basic structures. Some actuators have very simple shape, such as the SDA ( Scratch Drive Actuator), others have much more complex topology and are able to fulfil a complete function, specially for optical applications.
The SDA actuator proposed by Akiyama et al. [AKI 93], is a very simple structure, made of polysilicon, that is able to crawl on the substrate surface when it is cyclically biased. The structure and the operation principle of SDA are plotted in Figure 30.
The SDA is composed of a plate terminated by a bushing at one of its edge and is electrically isolated from the substrate by a thin dielectric layer, Figure 30(a). A SEM view is given in Figure 30(b) showing an individual SDA maintained to the anchor pad by mechanical links. Starting from the initial situation when the structure is grounded, Figure 30(c), a positive voltage pulse is applied to the SDA,...
