Small electronics powered directly with Wi-Fi signal
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Researchers have developed a technology that uses tiny smart devices known as spin-torque oscillators (STOs) to harvest and convert wireless radio frequencies into energy to power small electronics.
The amount of Wi-Fi sources has grown exponentially in recent years due to the boom in connected devices. Now a team from the National University of Singapore (NUS) believe they can make use of the excess signals available.
In their study, they have already successfully harvested enough energy using signals in the Wi-Fi band to power a light-emitting diode (LED) wirelessly, without using any battery.
“We are surrounded by Wi-Fi signals, but when we are not using them to access the internet, they are inactive, and this is a huge waste,” said Professor Yang Hyunsoo who led the project.
“Our latest result is a step towards turning readily-available 2.4GHz radio waves into a green source of energy, hence reducing the need for batteries to power electronics that we use regularly.
“In this way, small electric gadgets and sensors can be powered wirelessly by using radio frequency waves as part of the Internet of Things. With the advent of smart homes and cities, our work could give rise to energy-efficient applications in communication, computing, and neuromorphic systems.”
STOs are a class of emerging devices that generate microwaves, and have applications in wireless communication systems although their application is typically hindered due to a low output power and broad linewidth.
The research team came up with an array in which eight STOs are connected in series. Using this array, the 2.4GHz electromagnetic radio waves that WiFi uses were converted into a direct voltage signal, which was then transmitted to a capacitor to light up a 1.6-volt LED. When the capacitor was charged for five seconds, it was able to light up the same LED for one minute after the wireless power was switched off.
To enhance the energy harvesting ability of their technology, the researchers are looking to increase the number of STOs in the array they had designed. In addition, they are planning to test their energy harvesters for wirelessly charging other useful electronic devices and sensors.
The research team also hopes to work with industry partners to explore the development of on-chip STOs for self-sustained smart systems, which can open up possibilities for wireless charging and wireless signal detection systems.
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