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September 22, 2009 @ 11:13 am
Green Power from Piezoelectric Nanotechnology and Viral Batteries

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I don’t know about you but every time I charge a cell phone or use a laptop I wonder why we don’t have better batteries. It feels like a technological conspiracy that computer processing speed has doubled every 18 months for decades but battery life fails to do the same or come even close to that. If it had, we’d be flying around in battery-powered airplanes and maybe even sailing battery-powered cruise ships. Maybe the consumable nature of batteries prevents faster advances, but our existing batteries can be pretty inefficient, wasteful and often toxic.

I don’t expect the high seas to be filled with battery-powered ships anytime soon, but some very interesting developments are being made on a much smaller scale – the nanoscale in fact. This CNN article leads with the idea that you might be able to recharge your cell phone as long as you were walking. Nanoscale materials are very small; one nanometer equals one billionth of a meter and the scientists featured in the article are using structures that are 100 nanometers and smaller. These structures can be engineered with many interesting properties and performance characteristics such as efficient energy transfer.

The act of me typing this article right now is a release of energy stored inside my body but it is effectively wasted. Sound and heat are generated but the keyboard can’t harness the kinetic energy. In the future it may be able to. Zhong Lin “Z.L.” Wang and his team at Georgia Tech are utilizing the piezoelectric effect (“…the ability of certain materials to generate an electric potential when a stress is applied to them. For instance, if you compress a crystal, it temporarily changes shape, causing the ions inside the crystal to polarize and produce a voltage drop.” The electron flow then produces an energy output.) present in environmentally friendly zinc oxide nanowires to make solar cells and nanogenerators that can utilize energy from any mechanical movement. In the walking example, the body produces 67 watts of mechanical energy that can be converted into 11 watts of electrical energy. The smaller amounts of energy produced by blood flow, breathing, etc. could be used to power medical implants such as glucose meters for diabetics.

piezoeffectAngela Belcher and her team at MIT are working on another exciting eco-friendly battery project – what I will term “viral batteries.” They have synthesized a harmless virus called M13 bacteriophage to act as a protein scaffold for assembling tiny batteries with non-toxic materials such as iron phosphate, cobalt oxide and gold. The virus is wire-shaped and measures only 10 nanometers across and when coated binds well with carbon nanotubes to create the cathode (the “+” charge) and anode (the “-“ charge) of the battery. During assembly the virus is not alive and cannot replicate. Once the battery constructs itself, just ten grams of material is enough for 40 hours of portable media player power (equivalent to 3 normal batteries in the same device). For their next trick the researchers are working on spray-on and stamp-on batteries.

BacteriophageCartoon

The battery revolution is in its infant stages. According to Lux Research work cited in the article, only 0.6% of nanotech revenues in 2007 came from energy and environment applications, and 1.8% is the prediction for 2015. It could be many years before these breakthroughs usurp significant general energy use, but near term applications hold promise and will certainly evolve. Ultimately integrating clean, long-lived electricity generation into everything that needs the energy is a holy grail but what a wonder it would be.

 Graphic Credits: Piezoelectric effect from www.piezomaterials.com and Bacteriophage from Molecular Nanomachines at the Department of Biochemistry, University of Zurich.

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