Engineers devise new battery

Mechanical and aerospace engineering professor Michael McAlpine and his team developed a new type of energy-generating device that can be powered by the human body. Their rubber films, made of silicone and a ceramic material known as lead zirconate titanate (PZT), capture mechanical energy from body movements and convert it to an electric current.

The technology opens up “a wide variety of exciting future directions,” McAlpine said in an e-mail.

The team created the films by “first fabricating PZT nanoribbons — strips so narrow that 100 fit side-by-side in a space of a millimeter” — and then printing the high-performance ribbons onto silicone rubber, McAlpine said.

The breakthrough balances the flexibility of rubber with the stability of ceramics in a hybrid material. PZT can convert up to 80 percent of mechanical energy into an electric current, but previous devices were simply too rigid to capture the movements of the human body.

Using small, implantable chips, the rubber could power biomedical devices like pacemakers and hearing aids. Larger sheets could be worn as an artificial skin and could power portable devices requiring more energy, like iPods or cell phones.

Mobile computing has seen major strides in recent decades, with faster processors and more compact hard drives ushering in laptops and, more recently, smart phones. But power sources and batteries have seen the slowest growth in the field, McAlpine said. With next-generation batteries, devices could last longer and perform higher-energy tasks then ever before.

McAlpine said the technology is roughly five to 10 years from production. But while rubber sheets powering pacemakers are still years away, Yi Qi, a postdoctoral researcher working with McAlpine, said the team hopes to develop a model that will be strong enough to power low-energy sensors within the next few months.

McAlpine said the human body is the “ideal source of power,” since humans already perform such basic tasks as walking, typing and breathing.

Christine Lee ’12 joined the project last summer to do research in “an innovative and exciting field,” she said in an e-mail.

Lee said the summer was “an invaluable opportunity to work with the team,” adding that she was able to “not only learn from the tangible results of the project, but also from the patience and determination that the project demanded.” Though she has not continued working on the project this year, Lee noted that she hopes to revisit the subject for her senior thesis.

Some of the rubber films’ most significant applications are in the field of medicine.

Qi said the new devices’ potential to cut medical costs was one of the reasons she joined the project.

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“Think about how much it costs for surgery to replace the battery for a pacemaker,” she explained.

“If we could replace those batteries with power directly harvested from the continual motion of the lungs, it could significantly improve the quality of life for patients” McAlpine noted.

McAlpine started on the project when he came to the University in September 2008. Since then, his team has grown to include Qi and both graduate and undergraduate students from Princeton, California Institute of Technology and Morehouse College.