Will WiFi be able to charge?
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- https://www.sohu.com/a/299387776_224832
- publisher
- Gordon
- Issue Time
- Jul 4,2020
Summary
Wireless charging isn't a new concept. Nikola Tesla, the "father of alternating current," painted a blueprint for wireless charging more than 100 years ago. Countless scientists are exploring wireless charging. However, most of the materials used for wireless charging devices is expensive and performance is unsatisfactory. These shortcomings limit the development of these devices in wireless charging.
The ubiquitous Wi-Fi signal has given scientists new inspirations.
In fact, in addition to the WiFi signal, there is a lot of energy 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".
It is difficult to capture stray energy, but wifi signals are high-frequency electromagnetic waves, and everywhere around us. If we use rectifier diode antennas to receive wireless network signals and convert them into direct current through rectification and filtering, we can use them.
Recently, scientists from the Massachusetts Institute of Technology, Madrid Polytechnic University and other research institutions published a paper in Nature, saying that Wi-Fi signals can be converted into electrical energy to charge electronic devices. This discovery has made breakthrough progress in wireless charging technology.
MoS2 flexible rectifier antenna
This rectifier antenna is mainly composed of rectifier diode and Wi-Fi band antenna. The antenna is used to receive Wi-Fi signals, and the rectifier diodes are used to convert energy and convert AC signals to DC. The rectifier used in this new rectifier antenna is not ordinary. It is made of molybdenum disulfide (MoS2) to connect different metal phases. It is a two-dimensional semiconductor material and is often used to make flexible semiconductor components.
After exposure to specific chemicals, the atoms of MoS2 can rearrange and transform from the semiconductor phase to the metal phase. It is because of this special semiconductor-metal structure that the rectifier can convert signals in the Wi-Fi band, while also reducing the parasitic capacitance and resistance of the circuit. The lower the parasitic capacitance and resistance, the higher the efficiency of the rectifier.
The researchers found in experiments that the maximum output power of this flexible rectifier antenna can reach 40% under the appropriate external conditions. In other words, if 100 watts of energy are supplied externally, this device can generate 40 watts of electricity. Although compared with other rigid rectifier antennas (silicon-based or gallium arsenide-based), the conversion efficiency is still low, but the price of MoS2 is relatively lower, and it is non-toxic and harmless. More importantly, the MoS2 rectifier antenna is completely flexible, which means that its area can be made large, directly covering the surface of the object. All kinds of characteristics make its application prospects wider, such as used in wearable devices, implanted medical devices, and even bendable mobile phones that are now very popular.
This research is a milestone in the development of wireless charging. With the deepening of research and the continuous optimization of devices, perhaps in the near future, we can really use the ubiquitous Wi-Fi signal to surf the Internet at high speed, and we can also use the Wi-Fi signal to quickly charge various electronic devices.