Page 225 - Mechanics of Microelectromechanical Systems
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212 Chapter 4
Figure 4.31 Tip displacement as a function of overlap length for an electrostatically-
actuated microcantilever
4 ELECTROMAGNETIC/MAGNETIC
TRANSDUCTION
The electromagnetic and magnetic effects are generally recognized to
produce larger forces at larger air gaps, compared to the electrostatic
actuation/sensing methods. In many MEMS designs, electromagnetic and
magnetic transduction methods are utilized concurrently in order to enhance
the performance of the microdevice.
4.1 Electromagnetic Transduction
The electromagnetic actuation and sensing are based on the interaction
between the electric current and an external magnetic field. Figure 4.32
shows a linear conductor carrying a current I, and placed in an external
magnetic field B. The Lorentz force that corresponds to this interaction is
defined by the vector product:
and its magnitude is:
where l is the length of the conducting wire and is the angle between the
directions of I and B. As Eq. (4.58) indicates, the vectors B and Il need to
make a non-zero angle in order that a Lorentz force be produced.
