As technology advances, various electronic devices have come into use, and the number of these devices continues to increase. IoT (Internet of Things) technology, which connects information about things around us to the Internet, is also advancing, and this trend is also expected to continue. Continuous increase of the number of electronic devices will give rise to the issue of how to supply power to a huge number of electronic devices. Then, power wiring connections, periodic charging, and battery replacement will become impractical in terms of physical space, time and labor. Therefore, energy harvesting technology that generates power independently using minute energy in the environment is being developed. However, the energy used by conventional technology is not omnipresent, making it a challenge to realize technology that "can generate electricity anywhere."

A "hygroelectric cell" was developed by an AIST researcher. It can generate electricity using changes in the moisture in the air.

Development has been ongoing for many years for energy harvesting technology that uses minute energy present in the environment, such asthermoelectric conversion, photovoltaics, and vibration-based power generation, as stand-alone power supply for small electronic devices. However, locations with conventional energy sources such as heat, light, and vibration are limited, which made it difficult to say that this was technology that "can generate electricity anywhere." Therefore, energy harvesting technology is being developed that uses moisture (water vapor in the air) that exists nearly everywhere on the earth as an energy source. Conventional power generators that use moisture provide current on the nanoampere to microampere level, which cannot be a practical power supply. The newly developed hygroelectric cell operates on a new principle that combines deliquescent material and osmotic (salt concentration differential) power generation, and it has low internal resistance which enables continuous output of milliampere-level current. This cell can generate electricity using the difference in daytime and nighttime moisture simply by exposure to air. This technology is expected to apply an ultra-low power supply for IoT devices.