Batteries not needed?By Jim Collins • September 13, 2013
The day is coming when heartbeats power pacemakers, sneakers charge cell phones during a jog, and tires power their own pressure sensors as they rotate.
But the science is not quite there yet. The principle behind these future self-powered gadgets is called piezoelectricity; when certain types of crystals are squeezed, they generate electricity. Piezoelectric materials are already the magic behind self-igniting barbecue lighters, but the technology is limited by its low power output. Currently, most piezoelectric devices only produce power on the order of microwatts. (For comparison, a typical laser pointer shines about a 1000-microwatt light.)
“Piezoelectric materials have attracted little attention thus far due to the small amount of power they create,” said Argonne materials scientist Seungbum Hong. “But if we can improve this by a factor of 10 or 20, I envision it will change the game.”
Hong is leading an effort at Argonne to do just that. The research team is using atomic force microscopy to probe the internal structure and properties of piezoelectric materials, also known as “energy-harvesting materials.” Hong believes their work will result in improved materials that open the door to new applications in medicine, consumer electronics, and more.
The piezoelectric effect enables materials to convert “wasted” mechanical energy (like human motion, low frequency vibrations, or acoustic noise) into electrical energy. Upping the power potential could eliminate the need to replace batteries in small devices, resulting in technologies that are more energy-efficient, user-friendly, and environmentally friendly.
In the case of pacemakers, for example, this would mean doing away with the surgeries patients must undergo every five to seven years to replace batteries; hearing aid users wouldn’t have to buy new batteries every few weeks. On tires, a piezoelectric-powered sensor could monitor the tire’s pressure for the lifetime of a vehicle.
According to Hong, piezoelectric technology could also power wireless sensor networks to monitor the structural health of bridges and buildings.
“Mechanical engineers don’t like wires,” Hong said. “Going wireless would be more stable and likely less expensive.”
For large applications such as vehicles and bridges, these devices would be comprised of springs coated with an energy harvesting-polymer to capture and convert vibrations into electricity. Tiny biomedical devices need very small machines called microelectromechanical systems that use tiny polymer-coated levers to harness mechanical energy.
Read more about microelectromechanical systems and how they might be useful in smartphones »
The Argonne team, in collaboration with researchers at the Massachusetts Institute of Technology and the Korea Advanced Institute of Science and Technology, is focusing on a ferroelectric polymer called polyvinylidene fluoride because of its strong piezoelectric response.
“One of the simplest ways to improve poor performance is to identify and understand the strong and weak building blocks inside of materials,” Hong said. “By looking at the structure of atoms at the nanoscale, we can figure out how to get to a material that has the properties we need to increase power output.”
This research is supported by the U.S. Department of Energy’s Office of Basic Energy Sciences and the Brain Korea Program.