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5. Static response of MEMS 281
Figure 5.15 Two-beam thermal actuator with beam springs
where the 2 multiplier indicates there are two actuators and two restoring
springs. The actuation force for a two-beam thermal device was given in Eqs.
(5.34) as a function of the free displacement and bloc force which are
given in Eqs. (4.14) and (4.15) of Chapter 4 for the two-beam actuator. The
stiffness of a fixed-guided beam is:
Therefore, by solving for the output displacement in Eq. (5.43) gives
3.3 Torsion-Spring Microdevices
When a central mass is supported by two springs on the sides and the
actuation creates a torque about the hinge longitudinal axis, as shown in Fig.
5.16, the equilibrium equation corresponding to this situation gives the
rotation angle resulting from the interplay between actuation and the elastic
properties of the two hinges:
One common application of the microdevice of Fig. 5.16 is the so-called
torsion micromirror, which is sketched in Fig. 5.17 (a). As shown in Figs.
5.17 (a) and (b), a central plate is supported by two torsion hinges.
Electrostatic actuation by the plate of dimensions and will attract the
