Page 257 - Mechanics of Microelectromechanical Systems

244 Chapter 4
As the figure indicates, a voltage variation of about 1.2 V is necessary to
apply to a piezoelectric bimorph in order to achieve the same bending radius
as in a thermal bimorph which is subject to a temperature variation of 50°.

8.4 Piezomagnetic Bimorph

As discussed in the section introducing the piezomagnetic materials, a
component made out of such a material can either expand or contract about a
given direction as a function of the type of piezomagnetism (positive or
negative) and of the directional relationship between the polarization field
and the external magnetic field. In any situation, however, the amount of
strain is usually denoted by and is equal to:

Figure 4.53 Bimorph with positive piezomagnetic active layer: (a) external magnetic field is
parallel to polarization field; (b) external magnetic field is perpendicular to polarization field
When a piezomagnetic material is attached to a structural layer (in MEMS
this is generally done by magnetron sputtering) in a cantilever-type
configuration, the resulting bimorph can bend in the presence of an external
magnetic field. Figure 4.53 for instance shows a bimorph that contains a
positive piezomagnetic layer attached to a thicker structural layer. Assuming
that the piezomagnetic direction of polarization is parallel to the length of the