Batteries and chargers have been counted for days. That’s right if the researchers from the American university Massachusetts Institute of Technology (MIT) study the transmission of energy using signals from wi-fi.
“We are introducing a new way to power electronic systems in the future – by simply capturing wi-fi power in a way that can easily be integrated into comprehensive areas,” explains Tomás Palacios, a professor in the Department of Electrical Engineering and Computer Science at MIT, which has long devoted itself to studying more economical and intelligent forms of electric power.
The research was the subject of an article published Monday by the journal Nature.
Flexible Radio Frequency Antenna
Scientists have come up with the same idea of transformers capable of converting electromagnetic waves of alternating current into direct current electricity. In their model, they used a device with a flexible radiofrequency antenna, capable of capturing such waves.
This receiver was connected to a device made of an extremely thin two-dimensional semiconductor – just three atoms thick.
This semiconductor converts the signal into continuous electrical voltage, ready to power rechargeable batteries or, directly, electronic circuits. That is: the device does not have a battery, but it captures the signs of wi-fi present in the place and transforms them, passively, in electric current.
In laboratory experiments, scientists were able to get 40 microwatts of electricity when the device was exposed to the 150 microwatts of a conventional wi-fi network. It is more than enough electrical power to hold a tablet screen on or make small electronic chips work.
Use for medical purposes
This two-dimensional, flexible device format seems to excite researchers more. “What if we could develop electronic systems and involve a bridge or an entire highway? Or the walls of our office? We would bring electronic intelligence to everything around us,” predicts Palacios.
Among the uses of the system, besides day-to-day electronic devices, are the sensors for gadgets integrated to the so-called “internet of things”.
In the case of mobile phones, such a novelty comes against the advances of the industry in the design of flexible and increasingly thin devices.
The researcher Jesús Grajal, of the Technical University of Madrid, co-author of the study, recalls that it would also be possible to use the device for medical purposes. Not only to keep equipment powered from a day to day hospital but also to future gadgets that need to be very small for a conventional battery.
One example: researchers are currently developing pills that patients can swallow to accurately collect and transmit their health data – for diagnostic purposes. Such a solution of energy would be ideal in specific cases like this.
In these cases, concerns go beyond the size of conventional batteries. “The ideal is not to use batteries to power these systems, because if there is a lithium leak, the patient may die,” says Grajal. “In this way, it is much safer to harvest energy from the environment to connect these tiny laboratories inside the body.”
The material used by researchers to construct this efficient current transformer is MoS2, or molybdenum disulfide. It is an inorganic compound, which is found in mineral molybdenite – the main deposits are in the Czech Republic, Norway, Sweden, Australia, England and the United States.
The researchers created a MoS2 device with just three atoms thick enough to make it work, as one of the finest semiconductors in the world. This is because the atoms of the material behave in a particular way, rearranging themselves as a switch.
The researchers involved believe the material has the ability to capture and convert up to 10 GHz of wireless signals.
“This device is fast enough to cover most of the frequency bands used today, cellular signals, Bluetooth, wi-fi and many others,” says researcher Xu Zhang, lead author of the study.
The energy efficiency achieved with the model is 30%. The group now plans to test new models and materials to improve that potential and reduce energy loss.
In an interview with BBC News Brazil, Zhang explained that a long process for the device to get a commercial version is still necessary, that is, beyond the reach of the average user. “We need to develop a single device to a number of conversions and optimize the process as much as the design of circuit manufacturing. It will then be feasible to use something for electronic day to day,” he said.