Tiny generators developed at the University of Michigan could produce enough electricity to run a wristwatch or wireless sensor - just from the ambient vibrations in the air.
The Parametric Frequency Increased Generators (PFIGs) harvest energy from the vibration that's a byproduct of traffic driving on bridges and machinery operating in factories, for example.
Most similar devices have more limited abilities because they rely on regular, predictable energy sources, said professor Khalil Najafi.
"The vast majority of environmental kinetic energy surrounding us everyday does not occur in periodic, repeatable patterns. Energy from traffic on a busy street or bridge or in a tunnel, and people walking up and down stairs, for example, cause vibrations that are non-periodic and occur at low frequencies," he says.
The generators can produce up to 500 microwatts from typical vibration amplitudes found on the human body. That's more than enough energy to run a wristwatch, which needs between one and 10 microwatts, or a pacemaker, which needs between 10 and 50.
The team says the ultimate goal is to enable applications like remote wireless sensors and surgically implanted medical devices, where replacing batteries is difficult and expensive.
"There is a fundamental question that needs to be answered about how to power wireless electronic devices, which are becoming ubiquitous and at the same time very efficient," says Najafi. "There is plenty of energy surrounding these systems in the form of vibrations, heat, solar, and wind."