With the aging of the population and the progress of medical technology, the number of patients using implanted electronic devices such as artificial cardiac pacemakers and defibrillators is increasing all over the world. The Korean Academy of science and Technology (Kist) announced that the research team led by Dr. Song Xianzhe of the electronic materials research center has developed an ultrasonic wireless energy transmission charging technology that can be applied to human implants. This technology can also charge the batteries of underwater instruments such as sensors that monitor the condition of submarine cables. The relevant research was recently published in the journal energy and environmental science. When the battery of the pacemaker is low, the entire implant must usually be replaced by surgery. Therefore, scientists are developing a non-invasive battery charging system, which uses externally applied ultrasound to charge.

Electromagnetic induction and magnetic resonance can be used for wireless energy transmission. Electromagnetic induction is currently used in smartphones and wireless headphones. However, the limitation of its use is that electromagnetic waves cannot pass through water or metal, resulting in a short charging distance. Therefore, this method cannot be easily used to charge implantable medical devices. The magnetic resonance method requires that the resonance frequency of the magnetic field generator and the transmitting device are exactly the same, which has the risk of interfering with other wireless communication frequencies (such as Wi Fi and Bluetooth).

Considering these limitations, a team from the Korean Academy of science and Technology (Kist) announced that they had developed an ultrasonic power generator that could be applied to human implants. It uses the so-called triboelectric effect, in which some materials will be charged when they rub against each other, which is also the reason for the electrostatic charge when combing.

When ultrasonic wave is applied externally, it will cause the thin layer of ferroelectric material to vibrate back and forth between the two electrode layers, and finally generate current to charge the battery.

The Kist team uses ultrasonic waves instead of electromagnetic waves or magnetic fields as the energy transmission medium. Sonar using ultrasound is usually used in underwater environment. In various medical applications such as organ or fetal condition diagnosis, the safety of ultrasound in human body has been verified. However, the existing sound energy transmission methods are not easy to commercialize because of their low efficiency.

The research team developed a model that uses the triboelectric principle to receive ultrasonic waves and convert them into electrical energy, which can effectively convert small mechanical vibrations into electrical energy. By adding ferroelectric materials to the friction generator, the ultrasonic energy transfer efficiency is significantly improved from less than 1% to more than 4%. It can charge more than 8 MW at a distance of 6 cm, which is enough to operate 200 LEDs at the same time or transmit Bluetooth sensor data underwater. The newly developed device has high energy conversion efficiency and generates a small amount of heat.

Dr. Song said, "this study shows that electronic devices can be driven by ultrasound in a wireless charging way. If the stability and efficiency of the devices are further improved in the future, this technology can be applied to provide wireless power for implanted sensors or deep-sea sensors."

The mainstream wireless charging technology in the market mainly adopts three ways, namely electromagnetic induction, radio waves, and resonance. Qi adopts the most mainstream electromagnetic induction technology. In terms of technology application, Chinese companies have been at the forefront of the wireless charging industry. It is reported that Qi's domestic application products are mainly mobile phones. This is the first stage, and it will be developed and applied to digital products of different categories or higher power in the future.

However, there are two sides to everything. Although wireless charging technology has many attractions, it also has the limitations of current technology development and use demand. Although the equipment using wireless magnetoelectric induction charging can be invisible, and the wear rate of the equipment is low, the application range is wide, at the same time, the technical content is high, the operation is convenient, and the conversion of long-distance radio energy can be implemented relatively, the economic cost of the equipment is high, the maintenance cost will also increase, and the energy conversion efficiency of electromagnetic will decrease sharply with the increase of distance (the magnetic loss rate of electromagnetic space is too large), Although the subsequent technological development will gradually improve this problem, the long-distance use will still bring huge useless power loss.

However, wireless charging is destined to represent the future. Just like the development of communication mode from wired phone to mobile phone, fixed network to wireless Wi Fi, wireless may not be as powerful and stable as wired connection in terms of performance, but wireless technology will eventually become the mainstream in terms of practicality.

The future wireless charging technology will be more and more efficient and convenient. At present, the latest wireless charging technology, such as Wi Fi wireless charging (developed by the University of Washington in the United States), has been able to achieve effective power supply at a distance of 10 meters in the experimental stage; The brand-new ultrasonic wireless charging, the technology's sponsor company ubeam, has received a total of $1.7 million seed round financing, including Yahoo CEO Marissa Mayer, founders fund and Andreessen Horowitz; Focus light to charge (Microsoft Research), automatically locate electronic products and focus LED light to charge.

These new technologies have sprung up, constantly refreshing the feasibility and practicality of wireless charging technology. We have reason to believe that the future will be "wireless"!