Domestic researchers have realized a medical device called 'neural probe' that can be inserted into the brain and stimulate neurons (nerve cells) using micro organic light-emitting diodes (OLEDs). This presents a new treatment method for intractable brain diseases.
The Korea Advanced Institute of Science and Technology (KAIST) announced on the 6th that a research team led by Professors Choi Gyeong-cheol and Lee Hyeon-joo from the Department of Electrical and Electronic Engineering succeeded in developing a flexible micro OLED-integrated neural probe for optogenetics through joint research with Professor Jeong Eung-kyo's team from the University of Incheon.
The research results were selected as a cover paper in July for the international journal 'Advanced Functional Materials' in the field of nanotechnology.
Optogenetics is a technique that regulates neuronal activity by applying light stimuli of specific wavelengths to neurons. The neural probe is a medical device that stimulates when inserted into the brain.
According to the research team, micro OLEDs are flexible and can precisely deliver light to small areas, making them suitable for detailed analysis of brain circuits. Precise control of light wavelengths also allows for the study of complex brain functions. However, there are limitations to their use as bio-implanted devices due to degradation of electrical properties from bodily moisture and other factors. Optimizing the process of integrating them onto the probe is also a challenge.
The joint research team patterned an ultra-thin flexible encapsulation film made of aluminum oxide and parylene-C (Al2O3/parylene-C) into a thin probe form (260-600 micrometers (㎛)) to maintain biocompatibility. This increased the driving reliability of OLEDs in a biological environment rich in moisture and oxygen while minimizing tissue damage upon implantation.
Additionally, in the process of integrating high-resolution micro OLEDs, the same biocompatible material as the encapsulation film, 'parylene-C', was used to maintain the flexibility and biocompatibility of the entire device. This was followed by the introduction of a structural layer called 'pixel define layer' to independently drive eight micro OLEDs, eliminating electrical interference between adjacent OLED pixels and spatially separating each pixel.
In particular, the research team precisely controlled the residual stress and thickness of multiple thin film layers within the device to maintain its flexibility in a biological environment, allowing for insertion with a single probe without bending and without auxiliary devices like needles. Through this process, the research team successfully developed a flexible neural probe with micro OLED integration that has a significantly high level of optical output for optogenetics and biological tissue stimulation applications.
The research team demonstrated through trials that the low moisture permeability of the ultra-thin flexible encapsulation film, high performance in vivo, device lifetime lasting over 10 years, and individual driving of integrated OLEDs without electrical interference.
Dr. Lee So-min, who participated in the research, said, 'This study presents a new paradigm for the insertion of flexible OLEDs as measurement and therapeutic medical devices.'
References
Advanced Functional Materials (2025) DOI: https://doi.org/10.1002/adfm.202420758