Identifying the microscopic mechanism of vibrational energy harvesters

November 11, 2020

The Japanese research team elucidated the microscopic mechanism in which amorphous silica(1) becomes negatively charged as a vibrational energy harvester(2), which is anticipated to achieve self-power generation without charging, as it is needed for IoT that is garnering attention in recent years with its "trillion sensors" that create a large-scale network of sensors. Unlike wind power and solar power generation, vibrational power generation, which utilizes natural vibration for power generation, is not affected by weather.

Vibrational energy harvester that uses potassium ion electret, which the research group had previously developed, is of interest since it can operate semi-permanently. The potassium ion electret(3) is a vibrational energy harvester that uses introduction of potassium atoms in 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 mechanics calculations, the research group discovered that when potassium atoms are inserted in amorphous silica, electrons are provided 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. We discovered that this structure is what accumulates negative charge.

This result provides a design guidance toward improving reliability and longevity of vibrational energy harvesters. This would allow sensors that do not require charging, to become widely available, and contribute toward actualization of the internet of things (IoT)(4).

This study was jointly conducted by the research groups of professor Gen Hashiguchi of Faculty of Engineering, Shizuoka University and professor Hiroshi Toshiyoshi of Institute of Industrial Science, The University of Tokyo, along with professor Kenji Shiraishi, graduate student Toru Nakanishi, researcher Kenta Chokawa, and assistant professor Masaaki Araidai of Institute of Materials and Systems for Sustainability, Nagoya University, as part of JST Strategic Basic Research Programs. JST aims to create innovative basic technologies that convert unused microscopic energy in the environment into electric energy (energy harvesting). This result will be presented at the 37th Sensor Symposium "On Sensors, Micromachines and Applied Systems" (held online), titled "Investigation of negative charge storage mechanism in the potassium ion electret by first-principle calculation."
-end-
(1) Amorphous silica

Silica refers to any form of silicon dioxide (SiO2) consisting of silicon (Si) and oxygen (O). Quartz and quartz crystal are members of silica. Amorphous silica is where atomic arrangement of silica is quite random. It is often denoted as a-SiO2.

(2) Vibrational energy harvester

A system that converts natural vibrations (vibrations caused by vehicles in operation and people walking) to electrical energy. It can self-supply electricity and be used for various purposes without charging.

(3) Potassium ion electret

Electret is a charged object made of materials in which, as in magnetic polarization in permanent magnets, dielectric polarization remains in a dielectric even when the electrical field is lost. It was named electret in reference to magnets. Potassium ion electret is where a potassium atom is inserted into amorphous silica and then removed, which causes amorphous silica to be negatively charged semi-permanently.

(4) Internet of Things (IoT)

Various objects are connected to the Internet where these objects can mutually control each other through the Internet. This promises to move the digital society forward.

Japan Science and Technology Agency

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.