A power cell that directly converts mechanical energy to chemical energy – which can then be stored and converted to electrical energy – has been selected as one of 2012’s top breakthroughs in the physical sciences by Physics World magazine.

The cell, developed at the Georgia Institute of Technology by Professor Zhong Lin Wang and his research team, was first reported in the journal Nano Letters on August 9, 2012. By eliminating the need to convert mechanical energy to electrical energy for charging a battery, the new hybrid generator-storage cell utilizes mechanical energy more efficiently than systems using separate generators and batteries.

At the heart of the self-charging power cell is a piezoelectric membrane that drives lithium ions from one side of the cell to the other when the membrane is deformed by mechanical stress. The lithium ions driven through the polarized membrane by the piezoelectric potential are directly stored as chemical energy using an electrochemical process.

By harnessing a compressive force, such as a shoe heel hitting the pavement from a person walking, the power cell generates enough current to power a small calculator. A hybrid power cell the size of a conventional coin battery could power small electronic devices – and could have military applications for soldiers who might one day recharge battery-powered equipment as they walked, said Wang, who is a Regents Professor in the School of Materials Science and Engineering.

The Physics World team selected the project from more than 350 news articles about advances in the physical sciences published on physicsworld.com in 2012. The criteria for judging included:

• Fundamental importance of research
• Significant advance in knowledge
• Strong connection between theory and experiment
• General interest to all physicists

The full list of advances can be seen here. original Physics World article on the power cell can be read here.