High-performance, compact vibrational energy harvester created for self-charging portable devices

Walking can boost not only your own energy, but also, potentially, the energy of your portable electronic devices. Scientists at Osaka Metropolitan University have taken a significant step towards self-charging wearable devices with their invention of a piezoelectric vibration energy harvester enhanced by a dynamic magnifier that can amplify the power generated by impulsive vibrations. , such as human walking, by about 90 times, while remaining as small as currently developed energy harvesters. The results were published in Applied Physics Letters.

Nowadays, people carry multiple electronic devices such as smartphones, and wearable devices are expected to become more and more mainstream in the near future. The resulting demand for more efficient charging of these devices has increased attention to energy harvesting, a technology that converts energy like heat and light into electricity that can power small devices. A form of energy harvesting called vibrational energy harvesting is considered very practical as it can convert the kinetic energy of vibrations into electricity and is not affected by weather or climate conditions.

A research team led by Associate Professor Takeshi Yoshimura of the Graduate School of Engineering at Osaka Metropolitan University has developed a piezoelectric vibrational energy-harvesting microelectromechanical system (MEMS) only about 2 cm in diameter with a U-shaped metal component called a dynamic magnifier. . Compared to conventional harvesters, the new harvester enables an approximately 90-fold increase in power converted from impulsive vibrations, which can be generated by human walking motion.

The team worked on developing vibrational energy sensors that use the piezoelectric effect, a phenomenon in which specific types of materials produce an electrical charge or voltage in response to applied pressure. So far, they have succeeded in generating electricity at the microwatt level from constant-frequency mechanical vibrations, such as those generated by motors and washing machines. However, the energy output of these harvesters drops dramatically when the applied vibrations are non-stationary and impulsive, such as those generated by human walking.

In response to this challenge, the team developed and integrated the U-shaped vibration amplification component under the harvester. The component made it possible to improve energy production without increasing the size of the device. The technology is expected to generate electrical energy from unstable vibrations, including the motion of walking, to power small portable devices such as smartphones and wireless headphones.

Professor Yoshimura concluded: “Since electronic devices are expected to become more energy efficient, we hope that this invention will contribute to the realization of self-charging portable devices.”

Provided by Osaka Metropolitan University