Nowadays, it would be hard to not notice that electronic devices have become incredibly small. The use of miniature sensors in the upcoming Internet of Things (IoT) era could enable us to develop applications that were only seen in science fiction.
However, microelectronic devices still require power to run, and energy-harvesting micro-electromechanical systems (MEMS) can be used so that these minuscule contraptions can run on ambient energy, such as that coming from mechanical vibrations.
Conventional MEMS energy harvesters use an electret (the electrical equivalent of a permanent magnet; it has permanent charge stored in it) placed in an MEMS tunable capacitor, which has a moving electrode that is pushed by ambient forces, inducing the movement of charges. Unfortunately, this design is very constrained because the fabrication processes for both the electret and the MEMS components have to be compatible.
Therefore, a team of scientists, including Assistant Professor Daisuke Yamane from Tokyo Tech, proposed a new MEMS electret-based energy harvester that consists of two separate chips: one for the MEMS tunable capacitor, and one containing an electret and dielectric material to form another capacitor (see above). “This allows us to physically separate MEMS structures and electrets for the first time,” states Yamane.
Lead author Daisuke Yamane from Tokyo Tech (middle) with co-authors Hiroshi Toshiyoshi (left) and Hiroaki Honma (right) from University of Tokyo