Modern humans are power-hungry. Much of what we do requires electronic devices, most of which have to be charged. But what if you could just walk around while your device charged up automatically? Well, that dream is now a bit closer to reality thanks to a new breakthrough.
As reported in Nature, researchers have developed a system that connects a flexible antenna to capture radio waves to a two-dimensional semiconductor capable of converting the signals into usable direct current (DC) voltage. This can then be used to power circuits or recharge batteries. In experiments, the device was capable of producing 40 microwatts of power when exposed to typical Wi-Fi signals. That’s enough to run an LED or a silicon chip.
The system is called a rectenna and, in addition to using Wi-Fi, it is capable of using a significant range of radio waves that are currently unlicensed. This makes it an ideal system to integrate into flexible tech and wearable electronics. It could also be used in medical devices – both implantable ones and futuristic “smart pills”, which can be swallowed by patients and send diagnostic data to medical professionals.
“What if we could develop electronic systems that we wrap around a bridge or cover an entire highway, or the walls of our office and bring electronic intelligence to everything around us? How do you provide energy for those electronics?” study co-author Professor Tomás Palacios, from MIT, said in a statement. “We have come up with a new way to power the electronics systems of the future – by harvesting Wi-Fi energy in a way that’s easily integrated in large areas – to bring intelligence to every object around us.”
The innovation of the system is two-fold and the result of a molybdenum disulfide material that can be assembled into a sheet that's just three atoms thick. Its thinness allows it to be integrated into flexible systems and its parasitic capacitance – a phenomenon where certain materials store small amounts of electric charge, slowing down the circuit – is 10 times lower than in current systems. This allows the device to capture and convert radio waves of up to 10 gigahertz, covering the frequencies at which Wi-Fi operates.
“Such a design has allowed a fully flexible device that is fast enough to cover most of the radio-frequency bands used by our daily electronics, including Wi-Fi, Bluetooth, cellular LTE, and many others,” lead author Dr Xu Zhang added.
The team is currently planning to build more complex devices and focus on improving efficiency. The device has a 30 percent efficiency for converting Wi-Fi to electricity, a vast improvement on the 50-60 percent efficiency of traditional rigid silicon or gallium arsenide devices.