[Reading Science] World's First Implementation of an Ultrathin Device That Is Invisible and Self-Adheres to the Human Body

IBS, Sungkyunkwan University, and UNIST Joint Research Team Develops Transistor Based on 350 nm Nanomembrane
Stable Performance Maintained Even in Long-term Implantation

An ultrathin electronic device, invisible when placed on the skin and capable of seamlessly adhering to heart, muscle, and brain tissue, has been developed by a team of Korean researchers.

The joint research team from the Institute for Basic Science (IBS) Brain Science Imaging Research Group, Sungkyunkwan University, and Ulsan National Institute of Science and Technology (UNIST) announced on December 10 that they have successfully developed a self-adhesive nanomembrane, 'THIN (Transformable and imperceptible Hydrogel-elastomer Ionic-electronic Nanomembrane),' with a thickness of approximately 350 nanometers (nm), as well as an organic electrochemical transistor (THIN-OECT) based on it. They succeeded in real-time, high-sensitivity amplification and measurement of bio-signals on living tissue using this technology.

The results of this research were published online the same day in 'Nature Nanotechnology,' the most prestigious journal in the field of nanoelectronics.

Amplification of bio-signals through shape-transformable ultrathin bilayer transistor (THIN-OECT). Provided by the research team

The 350 nm nanomembrane 'self-adheres' to the heart, muscle, and brain... Signals are amplified on-site

The THIN developed by the research team fundamentally solves the 'complete tissue adhesion' problem that previous biosensors could not overcome. Living biological tissues are as soft as water and have many fine curves, making it difficult to attach devices stably. Traditional electrode-based measurements suffered from high signal noise, limiting precision, and even flexible devices revealed limitations in durability, manufacturing complexity, and long-term stability.

THIN is a precisely stacked structure of bioadhesive hydrogel and semiconducting elastic polymer at the nanometer scale. It is rigid and easy to handle when dry, but instantly softens and self-adheres to tissue upon contact with moisture. In experiments where THIN-OECT was attached to the heart, muscle, and brain of mice, the device enabled real-time, high-sensitivity, low-noise measurement of electrocardiograms, electromyograms, and brain waves. The device also demonstrated self-adaptability to tissue curvature and maintained stable function without inflammation or damage for more than four weeks in long-term implantation scenarios, proving its high biocompatibility.

The performance of this device is determined by the μC (ion-electron coupling gain) value, which reached 1034 F·cm－¹·V－¹·s－¹-the highest value ever reported among organic electrochemical transistors. This indicates a dramatic improvement in the efficiency of converting ion flow into electronic signals compared to previous devices, serving as a key indicator that enables real-time amplification of ultrafine bio-signals.

Just place it on-no need for fixtures, adhesives, or pressure

This research represents a significant advancement over existing bioelectronic technologies because THIN is the first platform to simultaneously satisfy three conditions. First, with a thickness of only 350 nm and greatly reduced flexural rigidity after hydration, the device is so thin and flexible that human tissue can barely perceive its presence.

Additionally, thanks to its moisture-responsive structure, simply placing it on tissue allows it to soften and conform within 10 seconds, exhibiting strong adhesion. Throughout this process, no adhesives, external pressure, or fixation structures are required.

Furthermore, THIN-OECT operates by amplifying signals directly at the site where bio-signals are generated (on-site amplification), maintaining a high signal-to-noise ratio (SNR) while minimizing external circuitry. These features enable stable, real-time measurements even in highly dynamic tissues such as the heart, muscles, and brain, overcoming the structural limitations of conventional biosensors.

The principle and characteristics of THIN's deformability, which adheres completely and firmly to tissue. The IBS Brain Science Imaging Research Group confirmed that THIN stretches flexibly without tearing even when softened by absorbing water. It also adheres to curved surfaces at the micron scale and has been proven to stably adhere to microstructures by mimicking mussel byssus. When THIN meets bodily fluids on the tissue surface, it gradually swells from one side and moves as if curling, during which its center of gravity shifts upward. As this change spreads, the entire nanofilm naturally adheres to the tissue's curved surface (Figure a). This principle is equally applicable under the dynamic conditions of heartbeats, confirming stable and firm adhesion (Figure b). Additionally, unlike existing devices with elastic substrates, THIN has low stiffness, allowing it to stretch naturally with the tissue while maintaining stable adhesion (Figure c). Provided by the research team

Opening the era of 'invisible electronic medicine'... Expansion to precision medicine, neuroengineering, and rehabilitation devices

Professor Son Donghee of Sungkyunkwan University stated, "This research has simultaneously solved the practical usability, durability, and tissue stability problems of conventional bioelectronic technology through an invisible nanoelectronic device that self-adheres to biological tissue. It can be expanded to various precision medical platforms, including heart disease monitoring, customized brainwave-based interfaces, muscle rehabilitation robot control, and electronic medicine-based stimulation therapy."

The research team plans to further advance the THIN platform by developing next-generation bio-interface systems. Their goals include developing multi-channel, high-density sensor architectures, implementing closed-loop sensor-stimulator circuits, and applying sensory feedback-type neuroprosthetic technologies. In the long term, they aim to evolve toward wireless, implantable, and biodegradable electronic medicine platforms.