Page 300 - Mechanics of Microelectromechanical Systems

5. Static response of MEMS 287

The horizontal displacement of the tip point 1, which moves to 1’ – as shown
in Fig. 5.20, is:

whereas the vertical displacement of the same point is:

Figure 5.20 Lever-based displacement amplification

At the same time, the displacement of the point 2, where the force F is
applied, is:

and therefore the displacement amplification, also called mechanical
advantage, can be calculated as:

Rotation joints, of the type sketched in Fig. 5.20, are rarely produced in
MEMS. A more convenient and often-applied solution is to utilize a flexure
hinge instead of a classical rotation joint, as discussed in Chapter 2.
Although the motion produced by a flexure hinge is not a pure rotation
and is also limited by the bending deformation capability of the flexure,
many MEMS designs implement it, especially due to its structural simplicity
and ease of microfabrication. Figure 5.21 shows two designs, which are the
flexure-based replicas of the lever of Fig. 5.20. The length of the flexure is
and its cross-section, generally rectangular, may be constant, or variable.