Reviewed by Matt Pullen, B.Sc.Apr 19 2022
The number of patients utilizing implanted electronic gadgets, such as artificial pacemakers and defibrillators, is growing globally as the population ages and medical technology advances. Currently, batteries for body-implanted devices are changed through incision surgery, which might cause health problems.
Schematic illustration of wirelessly charging a body-implanted electronic device using an ultrasonic probe. Image Credit: Korea Institute of Science and Technology.
As a result, a novel wireless energy transfer charging technology is emerging that may also be used to charge batteries of underwater equipment — like sensors — that are used to monitor undersea cable conditions.
A study group headed by Dr. Hyun-Cheol Song at the Electronic Materials Research Center created an ultrasonic wireless power transmission technique that may be used in the above-mentioned research fields, according to the Korea Institute of Science and Technology (KIST, President: Seok-Jin Yoon).
In wireless energy transfer, electromagnetic induction (EM) and magnetic resonance can be employed. EM induction is now employed in smartphones and wireless earbuds; however, it is restricted in its application due to the fact that EM waves cannot flow through water or metal, resulting in a small charging distance. Moreover, because the heat produced during charging is dangerous, this approach cannot be utilized to recharge implanted medical equipment.
The magnetic resonance technique necessitates that the magnetic field generator and transmitting device have the same resonant frequencies; also, there is a possibility of interaction with other wireless communication frequencies like Wi-Fi and Bluetooth.
As a result, instead of using EM waves or magnetic fields, the KIST group selected ultrasonic waves as an energy transfer channel.
Sonar, which employs ultrasound waves, is extensively employed in underwater environments, and the use of ultrasonic waves in the body has proved safe in a variety of medical applications, including organ and fetal condition diagnostics. However, due to acoustic energy’s low transmission efficiency, present acoustic energy transfer systems are difficult to market.
The study team created a model that efficiently transforms minor mechanical vibrations into electrical energy by receiving and converting ultrasonic waves into electrical energy by employing the triboelectric principle. The ultrasonic energy transfer efficiency was greatly enhanced by adding a ferroelectric material to the triboelectric generator, going from less than 1% to more than 4%.
Furthermore, charging with more than 8 mW power at a distance of 6 cm was feasible, which was enough to power 200 LEDs at the same time or send Bluetooth sensor data underwater. Importantly, the newly created device had a high energy conversion efficiency and produced only a little bit of heat.
This study demonstrated that electronic devices can be driven by wireless power charging via ultrasonic waves. If the stability and efficiency of the device are further improved in the future, this technology can be applied to supply power wirelessly to implantable sensors or deep-sea sensors, in which replacing batteries is cumbersome.
Dr. Hyun-Cheol Song, Electronic Materials Research Center, Korea Institute of Science and Technology
Journal Reference:
Kim, H. S., et al. (2022) Ferroelectrically augmented contact electrification enables efficient acoustic energy transfer through liquid and solid media. Energy & Environmental Science. doi.org/10.1039/D1EE02623B.