University of Michigan researchers, at their Engineering Research Center for Wireless Integrated Microsystems, have just created highly efficient some energy-harvesting devices that use the energy from surrounding arbitrary, non-periodic vibrations.
Such sources of vibration could be car traffic on bridges, machinery operating in factory, or humans as they move.
They called their little devices “Parametric Frequency Increased Generators” (PFIG). Khalil Najafi, chair of electrical and computer engineering, and Tzeno Galchev, a doctoral student, worked to develop three prototypes and planning to release the fourth.
In two of the generators they used magnetic induction, but in their latest – the smallest, measuring only one cubic centimeter – they used piezoelectric materials, like those found in modern lighters, that create extreme voltages when stressed mechanically. Using piezoelectric devices would enable the use in health monitoring.
The generators don’t produce much electricity, only 500 microwatts, if put to harvest human body movements.`A pacemaker would only need between 10 and 50 microwatts.
“The ultimate goal is to enable various applications like remote wireless sensors and surgically implanted medical devices,” Galchev said. “These are long lifetime applications where it is very costly to replace depleted batteries or, worse, to have to wire the sensors to a power source.”
Various piezoelectric energy harvesting devices had been built before, some of them already implemented in roads to pick up its vibrations, but because these are so sensitive they may have more subtle applications, like heath monitoring devices.