Power Bites: Personal Power

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!


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

Back to Top


  1. What is an electroactive polymer?
    [anno: An electroactive polymer is a man-made plastic that generates an electric charge when it is compressed or bent.]
  2. Why are electroactive polymers a useful invention when they are placed inside of a boot heel? Think about how the motion of walking affects the polymers and what the polymers do. Write a short paragraph about the usefulness of electroactive polymers placed in boots.
    [anno: Answers will vary but could include that electroactive polymers are useful because they can capture energy, such as the energy created by a person stepping down and compressing the polymer, that would otherwise be lost. This energy can then be used to power devices that the person might need, such as a GPS.]