Wireless power is often seen as the holy grail for mobile devices, allowing charging without being connected to a power source – or in some cases, without the need for an internal battery at all.
Researchers have had a breakthrough in making this a reality – publishing results in Nature – demonstrating advances in harvesting power from Wi-Fi signals and developing a rectenna (radio wave harvesting antenna) that’s thin and flexible – only a few atoms thick.
The important thing is the application of this rectenna. Because it’s so thin and flexible it could be applied to a wide range of technology – smart pills, mobile devices, wearables – allowing power harvesting without bulky design.
Electromagnetic waves contain power and there have been a number of methods used to harvest this power, all the way back to crystal radios a century ago, which took their power to operate from the radio waves they received.
Wi-Fi energy is harvested as AC, gathered by the semiconductor created from molybdenum disulphide combined with a Wi-Fi band antenna, and converted into usable DC energy. The team reports that 40µW of power can be harvested from a normal 150µW Wi-Fi signal, an efficiency of nearly 30 per cent.
There are existing rigid systems that will do the same – with higher efficiencies around 50 per cent – but the novelty here is the flexibility of the new system.
Talking of the potential applications for the new technology, Jesús Grajal, Technical University of Madrid and part of the research team, highlights the use for connected medical pills, saying: “Ideally you don’t want to use batteries to power these systems, because if they leak lithium, the patient could die … It is much better to harvest energy from the environment to power up these small labs inside the body and communicate data to external computers.”
Research will be continuing into how to make the system more efficient and allow it to be deployed in more complicated systems, but in reality, it will probably be some time before it becomes a consumer reality.
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