Energy-harvesting devices created at the University of Michigan Engineering Research Center for Wireless Integrated Microsystems are highly efficient at harvesting energy from non-periodic vibrations as from traffic driving on bridges, machinery operating in factories and humans moving their limbs.
The Parametric Frequency Increased Generators (PFIGs) were created by Khalil Najafi, chair of electrical and computer engineering, and Tzeno Galchev, a doctoral student in the same department.The researchers have built three prototypes and a fourth is forthcoming. In two of the generators, the energy conversion is through electromagnetic induction with a coil and magnet. The latest and smallest device, which measures one cubic centimeter, uses a piezoelectric material, which has applications in infrastructure health monitoring. U of M researchers say the generators could one day power bridge sensors that would warn inspectors of cracks or corrosion before human eyes could discern problems.
The generators have demonstrated that they can produce up to 0.5 mW (or 500 uW) from typical vibration amplitudes found on the human body. That's more than enough energy to run a wristwatch, which needs between one and 10uW, or a pacemaker, which needs between 10 and 50.
The university is pursuing patent protection for the intellectual property. A team of engineering and business students are working to commercialize the technology through their company, Enertia.
For more information:
Chief researcher Khalil Najafi: http://www.eecs.umich.edu/najafi/
Engineering Research Center for Wireless Integrated Microsystems: http://www.wimserc.org/