What the research is about
In factories, warehouses, and homes, small sensors that monitor temperature, human movement, and machine conditions are becoming increasingly common. These network-connected devices are collectively known as the Internet of Things, or IoT. While IoT technologies offer great convenience, their rapid growth has brought a serious challenge: how to supply power.
As the number of devices increases, replacing dozens of batteries or installing complex wiring becomes time-consuming and costly. To address this issue, researchers have turned their attention to wireless power transfer, a technology that delivers electricity without using cables.
Wireless power transfer using radio waves or microwaves has been studied for many years and is already used in familiar applications such as IC cards. However, transmitting sufficient power over distance requires large antennas, and much of the energy is lost along the way. For this reason, optical wireless power transfer, which uses light to deliver energy, has attracted growing interest. Laser-based systems can transmit power over long distances, but ensuring safety for human eyes and skin remains a major challenge.
From a safety perspective, LED lighting-already widely used in our daily lives-can be safely operated in spaces where people are present. In this research, invisible light such as near-infrared radiation is used for power transfer, reducing concerns related to glare and safety. However, LEDs have a drawback: their light spreads easily, causing energy to weaken rapidly with distance. Professor Tomoyuki Miyamoto and his colleagues at Institute of Science Tokyo (Science Tokyo) set out to answer a key question: Can safe LED light deliver electricity efficiently over longer distances?
Why this matters
The key innovation of this research lies in "smart control of light." The team developed a system using a shape-changing liquid lens that automatically adjusts how light spreads depending on the distance to the receiver. As a result, they succeeded in concentrating light efficiently to deliver power over distances of up to five meters-roughly the length of a typical room.
The researchers also addressed another major challenge: maintaining accurate power delivery under different lighting conditions. By combining an RGB camera-commonly used in smartphones and digital cameras-with an infrared camera, the system can instantly switch between detection modes. This allows the receiver's position to be tracked reliably even in complete darkness, ensuring that light is continuously directed to the correct location.
This high-precision image-processing technology prevents misalignment and interruptions in power delivery, representing a significant advance over previous optical wireless power systems.
What's next
If put into practical use, this technology could bring us closer to an IoT society free from the burden of battery replacement and complex wiring. Because it is safe for humans and animals, it can be used in indoor living spaces, farms, and other environments where safety is critical. Stable power delivery would also be possible at night or in locations without conventional lighting.
In the future, ceiling-mounted LED lights may serve not only as sources of illumination, but also as power supplies-forming a completely new type of infrastructure that supports everyday life.
Comment from the researcher
Light is an essential and familiar part of our daily lives. By using light as a source of energy, we can create new systems that support society. I hope people will look forward to the day when everyday light becomes a power source for a future without wires.
（Tomoyuki Miyamoto, Professor, Laboratory for Future Interdisciplinary Research of Science and Technology, Institute of Science Tokyo）
