Piezoelectric energy principles

Piezoelectricity is the operating principle of quartz watches. In these devices, a tiny crystal of quartz oscillates at a frequency of 32 kHz in response to an electrical charge generated from the battery. In general, the overall size and composition of a piezoelectric crystal will affect its oscillation frequency. Since quartz loses very little energy upon vibration, the integrated circuit (IC, see Chapter 4) within a watch is used to reduce the repeatable oscillations into electric pulses, which are displayed as hours, minutes, and seconds on the watch face. 

Nebilizers are among the oldest devices used for delivery of therapeutic agents.18 They employ energy from compressed gas or piezoelectric ceramics to generate droplets of water containing dmg. The principle of air jet dispersion is shown in Figure 16.1C. Dmg solution (or occasionally suspension) is drawn from a reservoir... 

Measurements of the surface tension and surface stress of solids are not easy. Some attempts have been made to measure the surface energy, or at least to determine the PZC, of solid electrodes attached to piezoelectric materials (36, 37). More often there is a reliance on studies of differential capacitance (Section 13.4.3) (35, 38). In principle, these measurements could provide all of the information needed to describe the surface charges and relative excesses however, one must first know the PZC. Evaluating it for a solid electrode/electrolyte system is not straightforward, and indeed, as discussed below, the PZC is not uniquely defined for a polycrystalline electrode. The most widely used approach is to evaluate the potential of minimum differential capacitance in a system involving dilute electrolyte. The identification of this potential as the PZC rests on the Gouy-Chapman-Stem theory discussed in Section 13.3,... 

Ambient air flow or forced convection can also be a source of energy for distributed environmental sensors or similar autonomous devices exposed to a flow. The airflow can induce the rotation of a microturbine (similar to large-scale wind mills) or the oscillation of a structure. This mechanical energy can then be converted to electricity by electromagnetic, piezoelectric, or electrostatic principles. 

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