Development that resonates

Abstract

Professor Chang Won Jung from Seoul National University of Science and Technology talks to us about his research on resonators. The team used copper wires optimise the transparent film resonators The need for charging electronic devices has been becoming a critical issue. As the number of portable devices has increased, due to the popularity of smart phones and tablets, the ability to conveniently charge them has become essential. In their laboratory in Seoul, researchers have improved on the current technology and applied it to other areas including wireless energy harvesting. This process is called wireless power transfer (WPT) and is a transmission method of electricity from a source to a load without conductors, usually via an electromagnetic field. There are two main types of wireless power transfer, Magnetic Resonance WPT (MR-WPT), and Magnetic Inductive WPT (MI-WPT). These rely on the occurrence of resonance magnetic coupling. In Magnetic Resonance WPT, electric energy is transferred in the magnetic field, whereas Magnetic Inductive WPT operates in the near field. Generally, the transfer efficiency of MI-WPT is higher than that of MR-WPT over short distances, but the transfer distance of MR-WPT is longer than that of MI-WPT. MI-WPT has been studied extensively and the technologies developed are now available commercially, including chargers for mobile devices. However, in the case of the MR-WPT, several problems remain and more research is needed before they can be used commercially. One of these problems is efficiency. By adding capacitors to the MR-WPT system the efficiency can be increased as the resonators correspond to the power energy at the same resonant frequency. The resonant frequency of the resonator depends on inductance and capacitance. For example, increasing the inductance and capacitance of the resonator reduces the resonant frequency. It is not easy to reduce the resonant frequency using inductance and keep the system small enough for mobile use. Adding capacitors adjusts resonant frequency and allows the system to remain small. Therefore, matching the resonant frequency between resonators could help to increase the transfer efficiency of MR-WPT system. Until now transparent WPT hasn't been widely researched because of its poor conductivity. The letter highlighted in this feature presents new advances in the field. The team looked into applications of transparent film resonators such as smart windows and mobile devices. They found that as the transparent WPT system needed be small it wasn't big enough to fabricate the WPT system on. They solved this problem by designing a new, compact, WPT system using copper. Their initial test samples performed badly but through precision processing and optimisation of fabricating conditions they improved the functionality of transparent WPT. This progress paves the way for future novel uses of WPT. Transparent WPTs are incredibly useful due to their transparency. It allows them to be placed anywhere where electricity is needed; from small sensors and mobile devices, to smart vehicles and smart windows. The team are now working on wearable WPT for biomedical sensors that are implanted in the human body and needed continuous energy to function. These sensors could be among the first applications of this project. The technology will allow advancements in smart objects such as phones and glasses The group have been improving transfer efficiency of WPT by changing materials and designing spiral patterns. To give free movements of WPT, they are now researching the alignment of WPT and how to compensate for when the WPT is out of alignment by using impedance matching and optimisation. There are many possibilities for the future use of WPT. WPT technologies could be widely used in various fields, not only in the electronic field but also medical and clothing fields. Professor Jung hopes that in the future many people will be using this technology in their everyday lives, as devices such as mobile phones or pacemakers would be able to charge anywhere.