Harvesting Vibrations with Piezoelectrics

　　從過往卡車的隆隆聲到電網(wǎng)的輕柔嗡嗡聲，每天都有振動的能量圍繞著我們。雖然設計工程師經(jīng)常被普通大眾視為一種煩惱，或者僅僅是背景噪音，但認識到這種能量正等待著在微功率電子學和傳感器中使用。

　　將振動轉換成電能的機會很多。車輛交通產生強烈的機械干擾。如果有任何疑問，你需要看起來比在你當?shù)氐牡缆房油莶贿h。腳步聲是另一個。即使是你走路時腳跟撞地的簡單動作也能產生幾瓦的能量。這兩種應用都有商業(yè)產品，壓電式收割正在建造于現(xiàn)代建筑的一些新的行人通道中。

　　飛機是另一個存在顯著振動的地方，可以方便地改造無線傳感器。壓電能量采集在這種類型的應用中提供了額外的檢測優(yōu)勢。例如，在一定的標定范圍內，結構元件的偏轉可以用來觸發(fā)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.