密歇根大学研制出一种可为无线传感器充电的设备，该设备从自然界的各种振动中获取能量。
与以往设备不同的是这种能量获取装置不需要特定频率的振动，而是可以利用自然界中的各种随机振动，譬如工厂机器的振动、桥梁的振动、人的走动等等。
密歇根大学的实验室已经研制出三种能量获取装置的模型，前两种采用电磁感应的方式，第三种采用压电物质。
第三种装置的体积可以做到1立方厘米左右，输出0.5mW，足够用来给手表或者检测桥梁状态的无线传感器供电。
密歇根大学在为这种技术申请专利（按本人查阅的信息看，密歇根大学并非第一个采用此方法获取能量，不过装置的小体积是一个不错的卖点）
ANN ARBOR, Mich.—Tiny
generators developed at the University of Michigan could produce enough
electricity from random, ambient vibrations to power a wristwatch, pacemaker or
wireless sensor.
The energy-harvesting
devices, created at U-M's Engineering Research Center for Wireless Integrated
Microsystems, are highly efficient at providing renewable electrical power from
arbitrary, non-periodic vibrations. This type of vibration is a byproduct of
traffic driving on bridges, machinery operating in factories and humans moving
their limbs, for example.
Most similar devices
have more limited abilities because they rely on regular, predictable energy
sources, said Najafi, who is the Schlumberger Professor of Engineering and also
a professor in the Department of Biomedical Engineering.
"The vast
majority of environmental kinetic energy surrounding us everyday does not occur
in periodic, repeatable patterns. Energy from traffic on a busy street or
bridge or in a tunnel, and people walking up and down stairs, for example,
cause vibrations that are non-periodic and occur at low frequencies,"
Najafi said. "Our parametric generators are more efficient in these
environments."
The researchers have
built three prototypes and a fourth is forthcoming. In two of the generators,
the energy conversion is performed through electromagnetic induction, in which
a coil is subjected to a varying magnetic field. This is a process similar to
how large-scale generators in big power plants operate.
The latest and
smallest device, which measures one cubic centimeter, uses a piezoelectric
material, which is a type of material that produces charge when it is stressed.
This version has applications in infrastructure health monitoring. The
generators could one day power bridge sensors that would warn inspectors of
cracks or corrosion before human eyes could discern problems.
The generators have demonstrated that they can produce up to 0.5
milliwatts (or 500 microwatts) from typical vibration amplitudes found
on the human body. That's more than enough energy to run a wristwatch,
which needs between one and 10 microwatts, or a pacemaker, which needs
between 10 and 50. A milliwatt is 1,000 microwatts.
更多信息可查询：
http://www.ns.umich.edu/htdocs/releases/story.php?id=7585