Harvesting Vibrations with Piezoelectrics

　　從過(guò)往卡車(chē)的隆隆聲到電網(wǎng)的輕柔嗡嗡聲，每天都有振動(dòng)的能量圍繞著我們。雖然設(shè)計(jì)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(rèn)識(shí)到這種能量正等待著在微功率電子學(xué)和傳感器中使用。

　　將振動(dòng)轉(zhuǎn)換成電能的機(jī)會(huì)很多。車(chē)輛交通產(chǎn)生強(qiáng)烈的機(jī)械干擾。如果有任何疑問(wèn)，你需要看起來(lái)比在你當(dāng)?shù)氐牡缆房油莶贿h(yuǎn)。腳步聲是另一個(gè)。即使是你走路時(shí)腳跟撞地的簡(jiǎn)單動(dòng)作也能產(chǎn)生幾瓦的能量。這兩種應(yīng)用都有商業(yè)產(chǎn)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(jī)是另一個(gè)存在顯著振動(dòng)的地方，可以方便地改造無(wú)線(xiàn)傳感器。壓電能量采集在這種類(lèi)型的應(yīng)用中提供了額外的檢測(cè)優(yōu)勢(shì)。例如，在一定的標(biāo)定范圍內(nèi)，結(jié)構(gòu)元件的偏轉(zhuǎn)可以用來(lái)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.