Harvesting Vibrations with Piezoelectrics

　　Harvesting Vibrations with Piezoelectrics

　　从过往卡车的隆隆声到电网的轻柔嗡嗡声，每天都有振动的能量围绕着我们。虽然设计工程师经常被普通大众视为一种烦恼，或者仅仅是背景噪音，但认识到这种能量正等待着在微功率电子学和传感器中使用。

　　将振动转换成电能的机会很多。车辆交通产生强烈的机械干扰。如果有任何疑问，你需要看起来比在你当地的道路坑洼不远。脚步声是另一个。即使是你走路时脚跟撞地的简单动作也能产生几瓦的能量。这两种应用都有商业产品，压电式收割正在建造于现代建筑的一些新的行人通道中。

　　飞机是另一个存在显著振动的地方，可以方便地改造无线传感器。压电能量采集在这种类型的应用中提供了额外的检测优势。例如，在一定的标定范围内，结构元件的偏转可以用来触发安全警告。

　　Although it is likely the most well known source of environmental energy thanks to the iconic windmill， wind， or even smaller indoor air currents can set up resonance vibrations in a thin cantilever beam. A piezoelectric device can， therefore， indirectly harvest wind energy.

　　Piezoelectrics are a subclass of crystals that are asymmetric. The asymmetry in the unit cell of the material sets up the mechanism whereby deforming the crystal leads to a small potential difference. The opposite is also true： applying an external voltage to the crystal will cause a mechanical deformation. For example， piezoelectric actuators are used in precision microscope stages such as those used in atomic force microscopy. Piezoelectric actuators on a smaller scale are used to squeeze ink out of some types of printing heads.