Piezoelectric actuatorsThe piezoelectric effect mentioned previously for use in force sensors also works in reverse. If a voltage is applied across a film of piezoelectric material, a force is generated. Examples of how this may be used are given in figure 15. In figure 15a, a layer of piezoelectric material is deposited on a beam. When a voltage is applied, the stress generated causes the beam to bend (figure 15b).
 Figure 15. The same principle can be applied to thin silicon membranes (figure 15c). When a voltage is applied, the membrane deforms (figure 15d). This, when combined with microvalves, can be used to pump fluids through a microfluidic system. One problem with piezoelectric devices is making the films thick enough that high enough voltages can be applied without dielectric breakdown (sparks / short circuits across the film). |