The increased popularity of wearable electronic devices has given rise to a number of techniques for extending relatively limited battery life.
“Energy harvesting is one such approach, converting ambient energy into electric energy utilizing such devices as onboard solar cells and piezoelectric generators,” reported EDN’s Paul Pickering. “TENGs are another.”
TENGs, also known as triboelectric nanogenerators, are used to convert mechanical energy into electricity. Essentially, a periodic contact and separation between two materials with various charge affinities acts as a charge-pump – alternately driving induced electrons to flow between the electrodes through an external load.
Image Credit: Georgia Institute Of Technology (via EDN)
Perhaps not surprisingly, researchers at the Georgia Institute of Technology are developing TENGs that could ultimately be capable of powering small electronics for wearable devices.
“Using four different modes of operation, they’ve harvested energy from a range of sources such as body motion, fabrics, vibrations from human walking, hand pressing, a shoe insole, vibration of a string or tree branch, machine vibration, elastic energy in a sponge structure, and sound waves in air and water,” said Pickering.
Meanwhile, researchers in Korea have reportedly developed a fully flexible, foldable wearable TENG with an output of 170V and 120uA (in a four-layer stacked configuration). The technology has apparently been used to power LEDs, an LCD display and a keyless vehicle entry system.
According to Patrick Gill, a Principal Research Scientist at Rambus, triboelectric and hybrid piezo/triboelectric generators harness the power of touch to bring digital circuits to life.
“They show a lot of promise as power sources for applications, which are expected to perform only when some force is applied,” he explained. “This means switches and buttons may become self-powered, pages on a physical book could generate power from page turns and your steps could power smart shoes.”
As a general trend, says Gill, increasingly sophisticated wireless IoT functionality is enabled by such progress.
“As energy generation, management and storage techniques provide more power, ever more efficient data radios – embedded processors and smart sensors require less of it,” he added.