Low-frequency vibrations can be energy-harvested, say researchers

February 07, 2014 // By Graham Prophet
Singapore-based researchers have reported success in harvesting vibrations to power microsensors; they are developing a means of efficiently harnessing low frequency vibrations as an infinite power source for miniature electronic devices.

Researchers from A*STAR’s Institute of Microelectronics (IME) say that low frequency vibrations – or infrasound – are, “the most abundant and ubiquitous energy source in the surroundings”. IME’s energy harvester continuously converts vibrations across a wide frequency range in different environments.

To use low frequency vibrations efficiently, common attempts focus on expanding the size of the device in order to attain maximum power output, which limit the applications of these energy harvesters. In addition, most reported designs can only operate at one fixed frequency, which significantly reduces the power generation efficiency in practical environments.

To address these design challenges, IME researchers have demonstrated an aluminium nitride (AlN) based energy harvester with record-high power density of 1.5 mW/cm 3 capable of generating electricity equivalent to three commercial implantable batteries* over a 10-year period.

The energy harvester also extends the flexibility of low frequency vibrational sources that can be harvested by extracting energy over the range of 0.1 Hz – 100 Hz. The wide sampling range makes it now possible to more productively harness real-world vibrational sources in spite of their irregularity and randomness.

Dr Alex Gu, Technical Director of IME’s Sensors and Actuators Microsystems Programme, who conceptualised the energy harvester design, commented, “Our design strategy exploits the coupling effect between the Vortex shedding and Helmholtz resonating in order to enhance the Helmholtz resonating and lower the threshold input pressure. By transferring the low frequency input vibrational energy into a pressurised fluid, the fluid synchronises the random input vibrations into pre-defined resonance frequencies, thus enabling the full utilisation of vibrations from the complete low frequency spectrum.”

* Comparison is calculated based on the energy generated from a 10-year usage of the energy harvester against that of a commercial implantable lithium battery with an energy density of 1.05 W.h/cm 3 and volume of 2.34 cm 3.

Institute of Microelectronics, A*STAR; www.ime.a-star.edu.sg