Power Bites: Personal Power

by Margaret A. Hill

Got a little brother with energy to spare? Maybe he could drive your CD player instead of driving you nuts! New inventions that convert human power into electricity make that notion a very real possibility.

Think about walking or jogging. The pressure of your foot striking the pavement is a form of mechanical energy. Several engineering groups are successfully building “heel-strike” mechanisms that will capture that mechanical energy and convert it into electrical energy. The key to this technology? Electroactive polymers. These human-made plastics generate an electric charge when they are compressed or bent. When placed inside the heel of a boot or shoe, electroactive materials become power generators as each step stretches and squashes them into performance.

Making these electricity generators function inside the boot heels of soldiers is the aim of engineers at SRI International in Palo Alto, CA, and at the Massachusetts Institute of Technology (MIT) in Cambridge, MA. The trick has been to develop a durable material capable of sufficient energy output that can be electronically interfaced with the devices needing power. SRI International has created a rugged electricity-generating material that meets these needs. When engineered into boot heels, the system is expected to generate enough electricity from eight hours of walking to power the wearer's communication device, GPS (global positioning system), and night vision goggles. Engineers at MIT are working on their own microscale version of an energy-harvesting system. It uses a mini-hydraulic mechanism to collect energy from foot pressure. This mechanism then supplies the degree of pressure needed to activate an electroactive material with high electrical output.

Both the SRI International and the MIT boot generators are months away from field-testing, but prospects look good. This new technology will eliminate batteries, lighten pack loads, and extend power availability. Not to mention—maybe?—be applied to little brothers with excess energy!

Vocabulary

hydraulic:: Of, involving, moved by, or operated by a fluid, especially water, under pressure.

SRI International

SRI International, the company that helped develop the electroactive polymer mentioned in the “Power Bites: Personal Power” article, has been developing technology in California for 60 years. The company was originally called Stanford Research Institute and was founded in association with Stanford University. Although the company is now independent from Stanford University, it is still a nonprofit company that focuses on research and innovation. Although you may not recognize the name of the institute, you have probably used some of their innovations. Did you know that way back in 1964, SRI developed the computer mouse? Today you might be printing pages at home thanks to SRI in the 1990s—SRI developed a line of ink cartridges that could be used by inkjet printers. SRI's work with robotic surgery led to a new way of operating on people. The institute even developed an oven surface that is easier to clean.

Now here's something that you may not know. SRI has been working with diamagnetic levitation. Diamagnetic levitation might be the next generation of magnetic levitation, or maglev. Magnetic levitation is used for many monorail trains. Maglev trains move forward through the use of electromagnets, which means that both electricity and magnets are needed to move the train. With diamagnetic levitation, no electricity is used to move an object. It's just magnets. In SRI laboratories, scientists have created a levitation system that is powered only by magnets. With this system, they have been able to lift more than 22 pounds, which is a world record. Now, the difference between moving 22 pounds and a train car is pretty big, but who knows what diamagnetic levitation might move in five years?

Vocabulary

diamagnetic:: Of or relating to a substance that is repelled by a magnet.
electromagnet:: A strong temporary magnet that uses electricity to produce magnetism.
levitation:: The state of rising and floating in the air in apparent defiance of gravity.

Sources:

Timeline of SRI International Innovations: http://www.sri.com/about/timeline
Diamagnetic Levitation: http://www.sri.com/esd/automation/diamagnetic.html