Nanogenerators to Enable Battery-Free Handhelds
Energy harvesting today is confined to a few niche applications, such as powering wireless sensor networks in remote areas where it is too expensive to send out crews to constantly be replacing batteries. However, by nano-sizing the working element in these energy harvesters, Northwestern University researchers claim their efficiency can be improved enough to enable battery-free mobile electronics.
Northwestern University researchers fabricated a micro-electro-mechanical system (MEMS) to test their piezoelectric nanowires
The most advanced semiconductor materials today are enabling advances in electronics that impact every segment of society—from consumer to IT. Gallium nitride (GaN), for instance, has enabled ultra-bright light-emitting diodes (LEDs) to replace automotive headlight filaments and Blu-ray drives to pack 50GB on a CD-sized disk. Now Northwestern University researchers claim that by nano-sizing gallium nitride and other piezoelectric semiconductors like zinc oxide (ZnO), their efficiency can be boosted by 20 to 100 times, thereby enabling battery-free electronic devices to enter the mainstream.
Piezoelectric materials, like GaN and ZnO, are structured as crystalline lattices of highly polarized molecules called dipoles where one end is positively charged and the other negatively charged. Whenever such a piezoelectric material is bent, or otherwise stressed, the distribution of these dipoles is reorganized, resulting in a momentary excess of charge that can be harvested as a current to drive electronic circuits. Since the deformation is usually cyclic—for instance, bending back and forth in sync with vibrations—the resulting voltage induces an alternating current. (This is in contrast to the direct current that comes from a battery.)
Source: Smarter Technology
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