Identification of the microscopic mechanism of vibrational energy collectors

A Japanese research team has elucidated the microscopic mechanism in which amorphous silica is negatively charged as a vibrational energy collector, which is expected to achieve autonomous power generation without recharging, as it is necessary for the IoT that is attracting attention. in recent years with its’ trillion sensors creating a large-scale sensor network. Unlike wind and solar energy, vibrational power generation, which uses natural vibrations for power generation, is not affected by weather conditions.

The vibrational energy harvesters using potassium ion electret, which the research team had previously developed, is interesting in that it can function semi-permanently. The potassium ion electret is a vibrational energy collector that uses the introduction of potassium atoms into the amorphous silica to create a negative charge on the amorphous silica. However, its microscopic mechanism was unknown, making it difficult to improve its performance.

Through quantum mechanical calculations, the research team found that when potassium atoms are inserted into amorphous silica, electrons are supplied from the potassium atom to the silicon atom. This causes the silicon atom to behave like a phosphorus atom. Silicon atoms form 5 covalent bonds with oxygen atoms instead of the usual 4, creating a SiO₅ structure. They found that this structure is what accumulates the negative charge.

This result provides design guidance for improving the reliability and longevity of vibrational energy collectors. This would allow sensors that do not require charging to become widely available and contribute to the actualization of the Internet of Things (IoT).

Provided by the Japan Science and Technology Agency