Every day, you use your mobile phone to connect to WiFi and open a web page, which seems to be commonplace. But have you ever thought that one day you might be able to charge with WiFi?
This sounds incredible, but there are studies that have proved its feasibility. Recently, foreign media reported a major breakthrough-scientists converted WiFi signals into electrical energy. In layman's terms, it is to generate electricity through WiFi. This means that in the future, there may be battery-free mobile phones, battery-free laptops ... There is no electricity, you can charge it when you connect to WiFi.
This technological breakthrough depends on the newly developed "silicon rectifier diode antenna". It can provide power for smart phones, laptops, wearable devices, etc. without batteries. According to reports, in this study, when the silicon rectifier diode antenna touched a WiFi signal of about 150 microwatts, it would generate about 40 microwatts of electricity.
So, how is the WiFi signal converted into electrical energy? Can electrical energy also be converted into WiFi signals? Can direct conversion be achieved between communication signals and energy?
WiFi signals are stray energy
In fact, in addition to the WiFi signal, there are many energy sources around us that can be converted into electrical energy. For example, radio waves, mechanical energy, human body thermal diffusion energy, etc. Such ubiquitous energy that has not yet been effectively used is called "stray energy".
There are many types of stray energy. Taking stray mechanical energy as an example, it includes the vibration energy generated by the components of the vehicle during travel, the energy generated by the vibration of the building caused by the movement or operation of heavy equipment, the kinetic energy generated by people stepping during walking, the swing of the arm and even Kinetic energy brought by changes in blood pressure. These seemingly insignificant sources of energy can be used.
"Capturing stray energy in the environment is like a bank collecting money from many small customers and lending it to those in need." Liu Guoqiang, a researcher at the Institute of Electrical Engineering of the Chinese Academy of Sciences, told Sci-tech Daily that the automatic watch that appeared in the middle of the last century The mechanical energy of the wrist swing makes the mainspring in the watch wind tightly, which in turn drives the watch to work.
However, the WiFi signal is different from other stray energy sources. It is a high-frequency electromagnetic wave. Considering its impact on human health, WiFi signals usually have very little energy within the range of human activity. A rectifier diode antenna is needed to receive the wireless network signal, and then it is converted to direct current through rectification and filtering before it can be used by us.
"Rectifier diode is a device that converts AC power into DC power, and it is also a 'bridge' where high-frequency electromagnetic signals are converted into DC power, that is, a 'bridge' where WiFi signals are converted into power." Liu Guoqiang said.
"At present, countries are gradually realizing the importance of stray energy, and this direction has become a research hotspot. The ultimate goal of research work is to partially replace or completely replace the existing chemical battery power supply in a mode of capturing stray energy. Liu Guoqiang introduced that if you can use stray energy to capture power generation technology, you may no longer need to replace the battery in the future. Scientists are expected to develop energy that does not need to be replaced for life, and may even make electrical appliances free from the constraints of power supply.
Take existing pacemakers for example. According to the data, the current pacemaker relies on battery power, but the battery life is limited, and the patient must replace the battery after a second operation within 5 to 10 years after installation. In the future, pacemakers can use the kinetic energy released by heartbeat to charge. Researchers have added a polymer sheet to an existing pacemaker to convert the kinetic energy of the heartbeat into electrical energy for the pacemaker to function normally.
It is still difficult to realize the interconnection of everything
Since stray network signals can be converted into electrical energy, is it possible that electrical energy can be converted into network signals, and then all things can be interconnected after being powered on?
"In theory, it is possible to connect everything with electricity," Liu Guoqiang explained. One possible way is to use electric energy to drive a high-frequency oscillator to generate a high-frequency signal, then amplify the signal through a high-frequency power amplifier, and then use The frequency multiplier, frequency converter, modulator and demodulator perform signal conversion, and then use the antenna to emit electromagnetic waves, which can realize the conversion of electrical energy into network signals.
"But there is currently no direct and simple means to convert stray energy into wireless signals." Liu Guoqiang said.
Despite the rapid development of stray energy capture technology, wireless communication technology and wireless energy transmission technology, it has become possible to convert energy and signals between objects within a certain range. But it will take time to achieve this goal. Among them, finding new materials and achieving technological breakthroughs in the field of materials is a major difficulty, and reducing the size of the power generation device and improving the conversion efficiency are the keys to the landing of the experimental results.
"Energy is an objective existence, just like tables and chairs. Ignite matches to generate heat, and speaking can generate vibration. But these energy cannot be directly converted into wireless signals." Wang Xiangru, associate researcher at the School of Optoelectronics Science and Engineering, University of Electronic Science and Technology, explained, Because the signal is orderly, if it is not modulated, the sound waves and electromagnetic waves we obtain are nothing but interference from the environment.
"The dissemination of information requires the two processes of encoding and decoding, as well as the code matching and agreement between the sending and receiving parties, otherwise we will not be able to understand the information." Wang Xiangru said, in this sense, the signal needs "special processing" Can be passed and acquired.
"At this stage, converting electrical energy into WiFi is just a good idea. Perhaps some day in the future, after some new materials appear, these stray energy sources can directly drive new devices and then emit signals." Liu Guoqiang said. (Dai Xiaopei)
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