research
< (Top, left to right) Dr. Haerim Kim (KAIST), Ph.D. candidate Ji Hong Kim (Hanyang University), student Jaewon Rhee (KAIST); (Bottom, left to right) Prof. Seungyoung Ahn (KAIST), Prof. Do Hwan Kim (Hanyang University) >
Wireless sensors used in wearable smart devices and medical equipment must be capable of detecting minute changes while maintaining high operational stability. However, existing technologies often utilize excessively high frequencies, leading to electromagnetic interference (EMI) or potential health risks to the human body. To address these fundamental issues, a Korean research team has developed a low-frequency-based wireless sensor technology.
A joint research team, led by Professor Seungyoung Ahn from the KAIST Cho Chun Shik Graduate School of Mobility and Professor Do Hwan Kim from the Department of Chemical Engineering at Hanyang University, announced the development of "WiLECS" (Wireless Ionic-Electronic Coupling System), a low-frequency wireless electrochemical sensing platform that combines ion-based materials with wireless power transfer technology.
Conventional wireless sensors suffer from low capacitance (the ability to store electrical charge), requiring high frequencies in the megahertz (MHz) range to compensate. However, these high-frequency methods can cause tissue heating or signal instability, limiting their practical application in clinical medical settings.
To solve this, the Hanyang University team developed a biocompatible ionic material with high capacitance, leveraging the movement of ions to store significant amounts of electricity. The KAIST team then integrated this with a wireless LC resonance system—a circuit that exchanges energy wirelessly. The result is a wireless sensor that operates stably within the human body at low frequencies.
Specifically, the team designed the system such that ions are attached to the surface of gold nanoparticles, inhibiting their movement under normal conditions and releasing them only when pressure is applied. This design causes a significant change in electrical storage even under minor stimuli. By monitoring these changes through fluctuations in the wireless frequency, the sensor can detect extremely subtle variations in pressure. The system demonstrates excellent performance even in the sub-1 MHz frequency band and achieves a high Signal-to-Noise Ratio (SNR) due to reduced electromagnetic interference.
In experiments using an artificial blood vessel model, the research team successfully monitored real-time blood pressure changes associated with arteriosclerosis—a condition where blood vessels harden or narrow. This demonstrates the technology's strong potential for future cardiovascular disease monitoring.
< Schematic Diagram of a Wireless Blood Pressure Monitoring Platform (AI-Generated Image) >
This study is significant as it shifts away from the conventional approach of simply increasing frequency to improve performance. Instead, it solves the problem by fundamentally altering the physical mechanism of sensor operation. It is evaluated as opening a new path for the design of next-generation bio-devices where electromagnetic safety is paramount.
Professor Seungyoung Ahn stated, "This research is a result of a collaborative effort combining ionic materials and wireless technology, overcoming the limitations of existing high-frequency wireless sensors. It has great potential for expansion as a platform that enables stable wireless sensing while minimizing electromagnetic impact."
The study, with Haerim Kim (KAIST) and Ji Hong Kim (Hanyang University) as joint first authors, was published in the world-renowned academic journal Nature Communications on March 11.
Paper Title: Low-frequency ionic-electronic coupling for energy-efficient noise-resilient wireless bioelectronics
DOI:
Authors: Ji Hong Kim (Hanyang University, Co-first author), Haerim Kim (KAIST, Co-first author), Jaewon Rhee (KAIST, Co-author), Joo Sung Kim, Hanbin Choi, Won Hyuk Choi, Yoseph Park, Jong Hwi Kim, So Young Kim, Seungyoung Ahn (KAIST, Corresponding author), and Do Hwan Kim (Hanyang University, Corresponding author).
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