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A Flexible Device That Converts Wi-Fi Signals into Electricity

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We can probably all agree that charging cables are just the worst and that we’d love to have fewer of them in our lives. Now, a new invention might give us just that: engineers have developed a flexible device that harvests energy from Wi-Fi signals. It can then convert it into electricity that could be used to power devices, wire- and battery-free.

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The device is what is known as a rectenna – a portmanteau of ‘rectifying antenna’ – which is a type of antenna that converts electromagnetic energy into direct current (DC).

The rectifying antenna:

The new rectenna, from a team led by MIT and the Technical University of Madrid, uses a radio-frequency antenna to capture electromagnetic waves (such as those produced by Wi-Fi) as alternating current (AC) waveforms.

wi-fi harvester
Source: Zhang et al./Nature

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These are sent to a two-dimensional semiconductor that converts them into DC, producing about 40 microwatts. It’s not much but is actually enough to power an LED or to drive silicon chips.

Because the rectenna is flexible, it can be deployed over large areas akin to wallpaper, or used in small, portable devices such as flexible smartphones, a field that is desperately trying to emerge. The tech could even be used in medical implants and swallowable sensors.

Old rectenna v/s the new one:

In previous rectennas, it’s been made from a material such as silicon or gallium arsenide, which is not only rigid but would also be expensive for large areas.

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What the team has done to improve on it is the use of a different material for the rectifier – the part that converts AC into DC. In the flexible rectenna, the team used Molybdenum disulfide (MoS2). It’s just three atoms thick, and, when exposed to certain chemicals, forces a phase transition between the semiconductor and metallic material. The structure is also known as a #Schottky diode, mimicking the properties of the metal-semiconductor junction used in rectennas previously – producing a working rectenna that minimises parasitic capacitance, resulting in higher speed.

This means it can capture higher frequencies than other flexible rectifiers, which can’t capture the GHz frequencies in which Wi-Fi operates.

This article is originally sourced from ScienceAlert, written by MICHELLE STARR 
Source / Journal Nature
Via / Provided by: ScienceAlert

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