Nanodevice Powered by Motion

April 25, 2010— -- Every move you make, every step you take, you can generate electricity. By cramming 20,000 nanowires into three square centimeters, scientists from Georgia Tech have created the world's first device powered solely by piezoelectric materials.

A piezoelectric material is something that, when pushed or pulled, generates a mild electrical charge. Within three to five years piezoeleectric nanowires, woven into a cotton shirt or housed in a shoe heel, could charge a cell phone or laptop battery after even a short walk.

"This is a key step to designing technology that will be useful in the near future," said Z.L. Wang, a professor at Georgia Tech and co-author of two new papers in Nature Nanotechnology and Advanced Materials.

Quartz and cane sugar crystals are common piezoelectric materials; when pressure is applied, a very small electrical current is produced. Over the last five to six years, however, scientists have worked with cheap zinc oxide and powerful lead zirconate titanate or PZT.

While the power generated from these materials has steadily risen into the millivolt range, it hasn't yet produced enough power to actually power a device. Now, according to the two new papers published by Wang's group at Georgia Tech, piezoelectrics can generate voltages up to 1.26 volts, and soon will produce voltages much higher than that.

Wang's group used plentiful and easy-to-manipulate zinc oxide nanowires to create their nanogenerator. An individual zinc oxide nanowire is so tiny that it's invisible to the human eye, measuring anywhere between 50 and 200 nanometers across and about five microns in length.

Twenty thousand nanowires, placed side by side and end to end, covers three square centimeters, with two thin electrodes hanging off either end.

This unique arrangement maximizes the electricity the piezoelectric nanowires can create. The wires work with each other, amplifying the electrical charge to record levels as the single layer is pushed back and forth with only the most slight and gentle of nudges.