Pusan National University develops one-step 3d microelectrode technology for neural interfaces

Microelectrode arrays (MEAs) are widely used for recording brain activity and stimulating neural tissues. However, conventional MEAs are typically flat, limiting their ability to conform to the natural curves of neural structures. Existing methods for adding 3D features require multiple fabrication steps, increasing complexity and restricting design possibilities.

To overcome these limitations, a team led by Associate Professor Joonsoo Jeong and Associate Professor Kyungsik Eom developed μETF, inspired by plastic thermoforming, a common technique for molding plastic sheets into different shapes. Their findings are published online on January 22, 2025, in the journal of npj Flexible Electronics. "The idea for this study came from a simple observation of plastic lids on take-out coffee cups. I realized that this plastic forming method could be applied at a microscopic level to create 3D structures for neural electrodes,” says Dr. Jeong.

The μETF method involves heating a thin, flexible polymer sheet embedded with microelectrodes and pressing it against a 3D-printed mold. The researchers used liquid crystal polymer (LCP) as the substrate due to its mechanical strength, biocompatibility, and long-term stability. This process forms precise protruding and recessed structures, enhancing the electrode's proximity to target neurons while preserving its electrical properties. Unlike traditional micromachining approaches, μETF simplifies fabrication and allows for a wide range of complex 3D structures, including wells, domes, walls, and triangular features, all within a single MEA.

In a proof-of-concept study, the researchers applied μETF to develop a 3D MEA optimized for retinal stimulation in blind patients. Computational simulations and lab experiments showed that the 3D electrodes reduced stimulation thresholds by 1.7 times and improved spatial resolution by 2.2 times compared to traditional flat electrodes. "Our 3D structures bring the electrodes closer to target neurons, making stimulation more efficient and precise," Dr. Eom explains.

Beyond retinal stimulation, the researchers see μETF being used in various neural interfaces, including those for the brain, spinal cord, cochlea, and peripheral nerves. notes Dr. Jeong. The method is capable of creating diverse 3D structures—including wells, domes, walls, and triangular features—enabling tailored electrode designs for different neural environments.

One promising future use of this technology is in brain-computer interfaces (BCIs), which could help restore movement in paralyzed patients. By implanting 3D neural electrode arrays in the motor cortex, we could decode neural signals and translate them into physical actions, like controlling robotic arms or wheelchairs.

The versatility of μETF extends beyond neural interfaces. The research team is exploring its potential in wearable electronics, organoid studies, and lab-on-a-chip systems, where precise 3D microstructures could enhance device functionality. The next step includes refining fabrication techniques for broader medical applications.

With its ability to enhance neural recording and stimulation while simplifying fabrication, μETF represents a major advancement in neuroprosthetic technology and neural rehabilitation treatments.

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Reference

DOI: 10.1038/s41528-024-00378-0

About the institute
Pusan National University, located in Busan, South Korea, was founded in 1946 and is now the No. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service, and has approximately 30,000 students, 1200 professors, and 750 faculty members. The university is composed of 14 colleges (schools) and one independent division, with 103 departments in all.

Website: https://www.pusan.ac.kr/eng/Main.do

About the author Associate Professor Joonsoo Jeong
Dr. Joonsoo Jeong is an Associate Professor of Biomedical Convergence Engineering at Pusan National University (PNU), Republic of Korea, since 2018. His group (Neuro & Bio Electronics) is focusing on neural interfaces where electronics meets neural systems, based on soft and flexible microelectronics. His team is developing implantable and wearable approaches for helping impaired sensory, motor and cognitive neural functions, as well as for multifunctional health monitoring. Before coming to PNU, he received BS, MS, and PhD in Electrical Engineering and Computer Science from Seoul National University. He was a postdoctoral researcher at Arto Nurmkikko’s lab at Brown University, USA.

About the author Associate Professor Kyungsik Eom
Dr. Kyungsik Eom is an Associate Professor of Electronics Engineering at Pusan National University (PNU), since 2019. His group (Neural Interface Lab) is focusing on developing safe and effective neural interfaces especially using electromagnetic energy. His team is interested in theoretical analysis of fundamental background of neural interface as well as experimental validation. He received BS in Electrical and Electronics Engineering at KAIST, and MS and PhD in Electrical Engineering and Computer Science from Seoul National University. He was a postdoctoral researcher at Brown University, USA.