Our eyes are set only on a narrow strip.possible wavelengths of electromagnetic radiation, about 390-700 nanometers. If you could see the world at different wavelengths, you would know that in an urban area you are even illuminated in the dark - infrared radiation, microwaves and radio waves everywhere. Part of this electromagnetic radiation from the environment is emitted by objects that scatter their electrons everywhere, and a part carries radio signals and Wi-Fi signals that underlie our communication systems. All this radiation also carries energy.
What if we could use the energy of electromagnetic waves?
Researchers from the Massachusetts technologyInstitute presented a study that appeared in the journal Nature, which described in detail how to begin the practical implementation of this goal. They developed the first fully bendable device that can convert energy from Wi-Fi signals to usable DC electricity.
Any device that can convertThe signals of alternating current (AC) to direct current (DC) are called rectal: rectifying antenna. The antenna picks up electromagnetic radiation, converting it into alternating current. It then passes through a diode that converts it into direct current for use in electrical circuits.
Rektenny were first proposed in the 1960s andeven used to demonstrate the model of a helicopter powered by microwaves in 1964 by inventor William Brown. At this stage, the futurists have already dreamed of wireless transmission of energy over long distances and even the use of rectilla to collect space solar energy from satellites and transfer to Earth.
Today, new technologies work in nanoscaleallow a lot of new. In 2015, researchers at the Georgia Institute of Technology collected the first optical rectenna capable of handling high frequencies in the visible spectrum from carbon nanotubes.
So far, these new optical rectennas havehave low efficiency, about 0.1 percent, and therefore cannot compete with the growing efficiency of photovoltaic solar panels. But the theoretical limit for rectenn-based solar cells is probably higher than the Shockley-Kusser limit for solar cells, and can reach 100% when illuminated with radiation of a certain frequency. This makes efficient wireless transmission possible.
A new piece of device manufactured by MIT,takes advantage of a flexible radio frequency antenna that can capture wavelengths associated with Wi-Fi signals and convert them to alternating current. Then, instead of the traditional diode to convert this current into a constant one, the new device uses a “two-dimensional” semiconductor, just a few atoms thick, creating a voltage that can be used to power wearable devices, sensors, medical devices or large-area electronics.
New rectennes consist of such “two-dimensional” (2D)materials - molybdenum disulfide (MoS2), which is only three atoms thick. One of its remarkable properties is the reduction of parasitic capacitance - the tendency of materials in electrical circuits to act as capacitors holding a certain amount of charge. In dc electronics, this may limit the speed of signal converters and the ability of devices to respond to high frequencies. New rectibene from molybdenum disulfide have parasitic capacitance an order of magnitude lower than those that have been developed so far, which allows the device to capture signals up to 10 GHz, including in the range of typical Wi-Fi devices.
Such a system would have fewer problemswith batteries: its life cycle would be much longer, electrical devices would be charged from ambient radiation and there would be no need to dispose of the components, as is the case with batteries.
“What if we could develop electronicsystems that will wrap around the bridge or which we will cover the whole highway, the walls of our office, and give electronic intelligence to everything that surrounds us? How will you provide all this electronics with energy? ”, Asks co-author Thomas Palacios, a professor of electrical engineering and computer science at the Massachusetts Institute of Technology. "We have come up with a new way to power the electronic systems of the future."
Using 2D materials allows cheapproduce flexible electronics, potentially allowing us to place it on large areas to collect radiation. Flexible devices could be equipped with a museum or a road surface, and it would be much cheaper than using rectenna from traditional silicon or gallium arsenide semiconductors.
Can I charge my phone by Wi-Fi signals?
Unfortunately, this option seems extremelyunlikely, although over the years the theme of “free energy” has been fooling people over and over. The problem is the energy density of the signals. The maximum power that a Wi-Fi access point can use without a special broadcasting license is usually 100 milliwatts (mW). These 100 mW are radiated in all directions, spreading over the surface area of the sphere, in the center of which is an access point.
Even if your mobile phone collected allthis power is 100% efficient, it would still take days to charge the iPhone, and the phone’s small area and distance to the access point would seriously limit the amount of energy it could collect from these signals. The new MIT device will be able to capture about 40 microwatts of energy when exposed to typical Wi-Fi density of 150 microwatts: this is not enough to power the iPhone, but enough for a simple display or a remote wireless sensor.
For this reason, it is much more likely thatWireless charging for larger gadgets will rely on induction charging, which is already able to power the devices up to a meter away, if there is nothing between the wireless charger and the charging object.
However, the surrounding radio frequency energycan be used to power certain types of devices - how do you think Soviet radios worked? And the upcoming "Internet of things" will definitely use these power models. It remains only to create sensors with low power consumption.
Co-author of the work, Jesus Grazhal from the TechnicalUniversity of Madrid sees potential use in implantable medical devices: a pill that a patient can swallow will transfer health data back to a diagnostic computer. “Ideally, I would not want to use batteries to power such systems, because if they miss lithium, the patient may die,” says Grazhal. "It is much better to collect energy from the environment in order to power these small laboratories inside the body and transfer data to external computers."
Current device performanceis about 30-40% compared with 50-60% for traditional rectenn. Along with such concepts as piezoelectricity (materials that generate electricity when physically compressed or stretched), electricity generated by bacteria and the heat of the environment, “wireless” electricity may well become one of the power sources for future microelectronics.
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