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Tham khảo tài liệu 'mechanics of microelectromechanical systems - n.lobontiu and e.garcia part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 198 Chapter 4 In the majority of MEMS applications the actuation force or the sensing signal are insufficient when only one pair of moving-fixed parts are being utilized. The practical solution to this problem is to couple several pairs of such mating members in a comb-type configuration. Figure 4.19 sketches an interdigitated pair with the main geometric parameters. The motion about direction 1 in this figure is usually referred to as parallel-plate whereas the other possible motion about direction 2 is generally named comb-finger motion. However the interdigitated designs are used for both motions and therefore in order to avoid confusion the alternative denominations of transverse and longitudinal will be used to indicate motions about the 1 and 2 directions respectively. These two types of motions are the main technological applications in planar MEMS and they will be presented in the following sub-sections. The potentially-variable distances between the moving and fixed parts are the gaps denoted by gx and gy in Fig. 4.19 in order to indicate the axis they refer to. Similarly the thickness of a fixed free member is indicated by either tx or ty depending on the axis. These two main directions of transductions are better indicated in Fig. 4.20. The guided supports are just a notional representation because pure roller bearings are rare in MEMS design. The motion directionality is rather achieved by using a proper spring suspension as the ones studied in the previous chapter. Figure 4.20 Main electrostatic linear transduction motions a Transverse b Longitudinal The transverse and longitudinal transduction principles will be presented next as well as another electrostatic method which uses microcantilevers for out-of-the-plane actuation sensing. It should be mentioned that the purpose of studying the actuation is to define the actuation force that is produced electrostatically whereas the objective of characterizing the sensing is to determine the capacitance .