尤其值得一提的是，Cagin和休斯顿大学的合作伙伴们找到了一种压电材料，在很小的尺度范围内，这种材料转换能量的效率能提升一倍。在这里，“很小的尺度”大概为21纳米厚。“但是，在这个尺度之外，无论是更大还是更小，该压电材料的能量转换效率都会大幅降低。”Cagin说。

    Cagin的这些研究发现刊登在美国物理学会的科学期刊《物理评论B》（Physical Review B）上。这一研究将在许许多多的低功耗电器中产生深远的影响，比如手机、笔记本电脑、对讲机以及其他各种与电脑相关的配件，而这些电器是每个人都离不开的，无论是普通消费者，还是法庭上的工作人员，甚至是战场上的士兵。

    1纳米等于1米的百亿分之一，是计量原子核分子尺度的单位，人的头发丝宽度相当于10万纳米。我们在很多高科技装置中都能见到纳米尺度的器件。

    虽然Cagin研究的东西非常小，但产生的影响却相当大。人们对各种便携无线设备的持续工作能力要求逐渐增高，而Cagin的发现则为这一领域的发展提供了巨大的支持。

    人们关心手机或MP3的各种功能，但他们更关注电池的寿命，因为这是让他们享受这些功能的关键。当然，除了能为消费者带来方便，自我供电装置同样是各个国家机构关注的焦点。

    美国国防高级研究计划署（DARPA）对士兵们在战场上使用发电装置进行了研究，开发出了能将行走产生的能量转换为电能的装置，为士兵们随身携带的设备发电。传感器（例如用于探测地雷的感应器）将极大地受益于这种自我供电系统，从而降低对电池的需求。

    “如果对这些压电材料进一步加工，它们甚至可以将各种扰动的声波，如气体、液体和固体的压力波，转换成为纳米或微米器件所需的电能。”Cagin说。

    压电体（piezoelectrics）是这项技术的关键，Cagin解释说。这个单词来自希腊文“piezein”（压力的意思），压电体指的是一种能将施加在它表面的机械力转换为电能的材料，通常是是晶体或陶瓷。相反地，当对这些材料施加电场的时候，它们的物理性能将发生变化。

    压电体最早是有法国科学家在19世纪80年代发现的，因此不是一个新概念了。在第一次世界大战期间，压电材料首次被应用到声纳装置中。今天，我们在麦克风、石英表中都有应用。汽车中的点烟器里同样含有压电材料。压下点烟器按钮后，压力将使压电晶体提供足够的电压来产生火花。

    大型场所也在使用压电材料。欧洲一些夜总会也将压电材料应用到了舞池中，这样就可以将跳舞者的脚步对地面的压力转换为电能。此外，香港的一家健身馆也用相同的方法来为室内的照明以及音响供电。

    “压电效应在这些领域大放光芒的同时，科学家们也开始致力于它在纳米尺度的应用，这是一个相对较新的领域，与以往不同，也更加复杂。”Cagin说。

    Cagin表示：“我们正在研究自然界的一些基本规律，并希望利用这些规律来研制更优秀的工程材料。我们研究它们的化学成分及物理构成，希望能控制它们，来提升材料的性能。”（申宁馨）

ScienceDaily (Dec. 2, 2008) — Imagine a self-powering cell phone that never needs to be charged because it converts sound waves produced by the user into the energy it needs to keep running. It's not as far-fetched as it may seem thanks to the recent work of Tahir Cagin, a professor in the Artie McFerrin Department of Chemical Engineering at Texas A&M University.Utilizing materials known in scientific circles as "piezoelectrics," Cagin, whose research focuses on nanotechnology, has made a significant discovery in the area of power harvesting – a field that aims to develop self-powered devices that do not require replaceable power supplies, such as batteries.

Specifically, Cagin and his partners from the University of Houston have found that a certain type of piezoelectric material can covert energy at a 100 percent increase when manufactured at a very small size – in this case, around 21 nanometers in thickness.

What's more, when materials are constructed bigger or smaller than this specific size they show a significant decrease in their energy-converting capacity, he said.

His findings, which are detailed in an article published this fall in "Physical Review B," the scientific journal of the American Physical Society, could have potentially profound effects for low-powered electronic devices such as cell phones, laptops, personal communicators and a host of other computer-related devices used by everyone from the average consumer to law enforcement officers and even soldiers in the battlefield.

Many of these high-tech devices contain components that are measured in nanometers – a microscopic unit of measurement representing one-billionth of a meter. Atoms and molecules are measured in nanometers, and a human hair is about 100,000 nanometers wide.

Though Cagin's subject matter is small, its impact could be huge. His discovery stands to advance an area of study that has grown increasingly popular due to consumer demand for compact portable and wireless devices with extended lifespans.

Battery life remains a major concern for popular mp3 players and cell phones that are required to perform an ever-expanding array of functions. But beyond mere consumer convenience, self-powering devices are of major interest to several federal agencies.

The Defense Advanced Research Projects Agency has investigated methods for soldiers in the field to generate power for their portable equipment through the energy harvested from simply walking. And sensors – such as those used to detect explosives – could greatly benefit from a self-powering technology that would reduce the need for the testing and replacing of batteries.

"Even the disturbances in the form of sound waves such as pressure waves in gases, liquids and solids may be harvested for powering nano- and micro devices of the future if these materials are processed and manufactured appropriately for this purpose," Cagin said.

Key to this technology, Cagin explained, are piezoelectrics. Derived from the Greek word "piezein," which means "to press," piezoelectrics are materials (usually crystals or ceramics) that generate voltage when a form of mechanical stress is applied. Conversely, they demonstrate a change in their physical properties when an electric field is applied.

Discovered by French scientists in the 1880s, piezoelectrics aren't a new concept. They were first used in sonar devices during World War I. Today they can be found in microphones and quartz watches. Cigarette lighters in automobiles also contain piezoelectrics. Pressing down the lighter button causes impact on a piezoelectric crystal that in turn produces enough voltage to create a spark and ignite the gas.

On a grander scale, some night clubs in Europe feature dance floors built with piezoelectrics that absorb and convert the energy from footsteps in order to help power lights in the club. And it's been reported that a Hong Kong gym is using the technology to convert energy from exercisers to help power its lights and music.

While advances in those applications continue to progress, piezoelectric work at the nanoscale is a relatively new endeavor with different and complex aspects to consider, said Cagin.

For example, imagine going from working with a material the size and shape of a telephone post to dealing with that same material the size of a hair, he said. When such a significant change in scale occurs, materials react differently. In this case, something the size of a hair is much more pliable and susceptible to change from its surrounding environment, Cagin noted. These types of changes have to be taken into consideration when conducting research at this scale, he said.

"When materials are brought down to the nanoscale dimension, their properties for some performance characteristics dramatically change," said Cagin who is a past recipient of the prestigious Feynman Prize in Nanotechnology. "One such example is with piezoelectric materials. We have demonstrated that when you go to a particular length scale – between 20 and 23 nanometers – you actually improve the energy-harvesting capacity by 100 percent.

"We're studying basic laws of nature such as physics and we're trying to apply that in terms of developing better engineering materials, better performing engineering materials. We're looking at chemical constitutions and physical compositions. And then we're looking at how to manipulate these structures so that we can improve the performance of these materials."