KAIST Develops Ultra-Miniature Wireless Brain Implant 'Smaller Than a Salt Crystal'

An ultra-miniature wireless brain implant, smaller than a salt crystal, has been developed. Neural implant technology is essential for research and treatment of neurodegenerative diseases. Most notably, the newly developed wireless brain implant has demonstrated practical potential, not only by achieving a smaller and lighter form factor, but also by maintaining stable function inside the body over an extended period.

(From left) Sunwoo Lee, Adjunct Professor at KAIST, Aloysha Molnar, Professor at Cornell University. Courtesy of KAIST

KAIST announced on November 27 that the research team led by Professor Sunwoo Lee, Adjunct Professor of Materials Science and Engineering at KAIST and Professor of Electrical and Electronic Engineering at Nanyang Technological University (NTU), in collaboration with the team of Professor Aloysha Molnar at Cornell University, has developed an ultra-miniature wireless neural implant called MOTE (Micro-Scale Opto-Electronic Tetherless Electrode). The team succeeded in stably measuring brain waves for one year by implanting MOTE into the brains of laboratory mice.

Inside the brain, invisible micro-electric signals constantly flow, generating various mental activities such as memory, judgment, and emotion. Technology that can directly measure these signals wirelessly, without external connections, is considered a key element in brain research and in the treatment of neurological diseases such as dementia and Parkinson's disease.

However, conventional implants with thick wired structures have made long-term use difficult due to issues such as the induction of inflammation in the brain, degradation of signal quality, size, and heat generation.

To overcome these challenges, the joint research team fabricated ultra-miniature circuits based on conventional semiconductor processes (CMOS) and combined them with a self-developed ultra-fine micro LED, achieving extreme miniaturization of the device. In addition, they applied a special surface coating to enhance durability, allowing the device to withstand the biological environment for extended periods.

Through these processes, the developed MOTE achieved a thickness of less than 100 nm and a volume of less than 1 nanoliter, making it thinner than a human hair and smaller than a grain of salt, while still functioning as a brain implant. Among wireless neural implants reported to date, it is the smallest in the world.

Another strength of MOTE is that it is a completely wireless system that does not require a battery. The device generates power by receiving external light, detects brain waves, and then transmits the information back outside by encoding it onto a light signal using pulse position modulation (PPM).

This method dramatically reduces energy consumption and minimizes the risk of heat generation. In particular, it offers the advantage of long-term use without the need for battery replacement.

MOTE neural implant on a salt crystal (left), MOTE neural implant 296 days after being implanted in an experimental mouse (right). Provided by KAIST

The joint research team also conducted a year-long implantation experiment by inserting MOTE into the brains of mice. As a result, stable measurement of brain waves was possible over the long term, with almost no inflammatory response observed around the implant, and no degradation in device performance was detected.

This is recognized as the first clear demonstration that an ultra-miniature wireless implant can maintain normal function inside a living organism over the long term.

Professor Lee stated, "MOTE is significant not only for its miniaturization and lightweight design, but also because it is the world's first truly wireless ultra-miniature implant, which was previously only expected to be possible." He added, "Through this, our joint research team has demonstrated the technical potential to solve not only the 'known unknowns' that have been raised during the development and use of wireless neural implants, but also the 'unknown unknowns' that newly emerge during the actual development process."

He further noted, "This technology can be widely applied not only in brain science research, but also in areas such as monitoring neurological disorders and developing long-term record-based therapeutic technologies."

Meanwhile, the results of this study were published online in the international journal Nature Electronics on November 3.

This content was produced with the assistance of AI translation services.