Brain–computer interfaces (BCIs) have emerged as revolutionary technologies facilitating direct communication between brain activity and external devices. These systems enable researchers to monitor and interpret brain signals in real time, unlocking new possibilities for medical applications and neuroscience research.

The Challenge of Microelectrodes

Microelectrodes, the fundamental components of BCIs, are tiny, hair-like structures implanted in the brain to either record or stimulate electrical activity. Historically, these electrodes have faced significant challenges in balancing two critical requirements:

  • Conductivity: Rigid metal or silicon-based electrodes enable stable signal recordings but often damage delicate brain tissues.
  • Tissue Compatibility: Softer polymer electrodes reduce harm to brain tissue but suffer from poor signal transmission capabilities.

Innovation in Electrode Design

To address these challenges, a research team led by Associate Professor Jong G. Ok from the Department of Mechanical and Automotive Engineering at Seoul National University of Science and Technology and Dr. Maesoon Im from the Brain Science Institute at the Korea Institute of Science and Technology (KIST) developed a pioneering microelectrode design. This new microelectrode features:

  • Three-dimensional "forests" of carbon nanotubes (CNTs) that conduct electricity efficiently.
  • Embedding within an elastic polymer base, making the design approximately 4,000 times softer than silicon and about 100 times softer than polyimide.

The findings of this study, which showcase a significant advancement in electrode technology, were published online in Advanced Functional Materials on June 27, 2025.

Fabrication and Electrical Performance

For the fabrication of these hybrid arrays, researchers utilized a multi-step process that includes the vertical growth of CNTs combined with a proprietary hybridization technique of CNTs and polymer. The resulting arrays exhibited:

  • Stable insertion into brain tissues.
  • Precise recording capabilities for visual response data.
  • A marked reduction in inflammatory responses as compared to traditional tungsten microwires.

Figure 1: Dual Functionality of CNT Microelectrode Arrays

“By combining the vertically aligned CNTs with a flexible polymer, we achieved both high electrical performance and mechanical compliance within one device,” states Dr. Ok. “This dual capability enables a long-term, stable neural interface without harming the surrounding tissue.”

Experimental Validation and Results

In vivo experiments conducted on mice demonstrated the device's ability to successfully record light-evoked responses from neurons within the visual cortex. Notably, implantation of CNT arrays over one month led to:

  • Lower activation of astrocytes and microglial cells compared to conventional electrodes, highlighting improved long-term compatibility.

Potential Applications of Hybrid Electrodes

The promising nature of these CNT hybrid arrays opens up various avenues for application:

Application Description
Visual Prosthetics Potential use for patients suffering from retinal degeneration or optic nerve damage.
Cortical Implants Development of tools for studying visual processing in neuroscience.
Brain-Assisted Communication Enhancements in technology to read visual attention and improve interaction with devices.

Future Directions

Researchers are now working to scale down the arrays to subcellular dimensions, which will allow for:

  • Higher resolution recordings directly from neurons.
  • Inspiration for next-generation bioelectronic devices that could restore or enhance vision through direct brain connectivity.

Conclusion

The advancement in flexible CNT-polymer hybrid arrays represents a significant breakthrough in the field of brain-machine interfaces. By overcoming previous limitations associated with traditional electrodes, these innovative devices hold the potential to revolutionize treatments for visual impairments and improve the quality of life for individuals with neurological disorders.

For further reading, refer to the study by Hyeonhee Roh et al titled Polymer‐Incorporated Mechanically Compliant Carbon Nanotube Microelectrode Arrays for Multichannel Neural Signal Recording, published in Advanced Functional Materials (2025).

To explore more, visit the full article at Science X.

References

  • [1] Hyeonhee Roh et al. (2025). Polymer‐Incorporated Mechanically Compliant Carbon Nanotube Microelectrode Arrays for Multichannel Neural Signal Recording. Advanced Functional Materials.
  • [2] Advanced Functional Materials. DOI: 10.1002/adfm.202509630