Development of a hybrid neural probe combining MicroLEDs and neural Electrodes

Overview

A research team led by Associate Professor Hiroto Sekiguchi and graduate student Gota Shinohara from the Department of Electrical and Electronic Information Engineering at Toyohashi University of Technology, in collaboration with Professor Takuya Sasaki and Project Researcher Tasuku Kayama from Graduate School of Pharmaceutical Sciences, Tohoku University, has successfully developed a hybrid neural probe that integrates MicroLEDs with neural electrodes. This innovative device enables precise control of neural activity and simultaneous multi-site recording within deep biological tissues.

In recent years, optogenetic techniques (Note 1) have enabled the control of neural activity by applying light externally to the organism. However, conventional optical fiber-based methods are limited to controlling single groups of neurons and face challenges in independently manipulating multiple neural regions with precision. Furthermore, the use of light stimulation alone is insufficient to fully elucidate the complex mechanisms underlying neural network information processing and signal propagation. As a result, there is a strong demand for technologies that integrate light stimulation with high-resolution recording of neural activity.

To address these challenges, our research team developed a novel hybrid neuroscience probe by integrating multi-point MicroLEDs with neural electrodes using a proprietary bonding technique. This hybrid probe enables simultaneous light stimulation and neural activity recording. Using this device, we successfully observed neural responses induced by light stimulation in the mouse brain with high spatial and temporal resolution. These findings mark a significant step forward in understanding neural network dynamics and offer new opportunities for developing treatments for neurological disorders as well as advancing neuroscience research.

The results of this study were published online in Applied Physics Express on 2, 10, 2025.

Details

Optogenetic techniques, which utilize light-sensitive proteins to control specific neural activities, have gained significant recognition as powerful tools in neuroscience research. However, traditional optical fiber-based methods are mainly suited for controlling single groups of neurons and are not capable of independently and simultaneously manipulating multiple neural groups.

In contrast, multi-point light stimulation devices employing MicroLEDs, which have attracted considerable attention in recent years, enable the individual control of multiple neural groups. This technological advancement is expected to significantly enhance our understanding of the dynamics of neural networks. However, light stimulation alone cannot fully unravel the mechanisms of information processing and propagation within neural networks, leading to increasing demand for technologies that integrate light stimulation with neural activity recording.

In our study, we developed a needle-shaped hybrid device that integrates MicroLEDs and neural electrodes, allowing for simultaneous light stimulation and neural activity recording deep within biological tissues. The MicroLED probe facilitates targeted light delivery, while the neural electrode probe records electrical signals from neural activity. Each probe was fabricated independently, and a proprietary bonding technique was used to align and connect the probes with high precision through gold (Au) micro-bumps. This advanced bonding technology enabled the precise adjustment of the gap between the LED and electrode at a resolution of 10 micrometers, achieving superior spatial resolution. Furthermore, the angular deviation between the probes was controlled to within 0.02°, ensuring excellent parallel alignment and enabling smooth insertion into deep brain regions of mice.

The hybrid probe, featuring six MicroLEDs and six neural electrodes, was successfully inserted into the mouse brain. This enabled precise light stimulation of specific brain regions and the accurate recording of neural activity in the surrounding areas.

Future Outlook

This hybrid probe addresses the spatial limitations of conventional optogenetic techniques and achieves high-precision control and recording of neural activity. It is expected to serve as a powerful tool for advancing our understanding of neural networks and holds promise for the development of new treatments for neurological disorders. Efforts will focus on further enhancing the probe's capabilities for multi-point stimulation and recording, aiming to contribute to practical applications in neuroscience research and the medical field.

Reference

Gota Shinohara, Tasuku Kayama, Ayumu Okui, Wataru Oda, Atsuhi Nishikawa, Alexander Loesing, Nahoko Kuga, Takuya Sasaki, Hiroto Sekiguchi (2025). Hybrid Probe Combining MicroLED and Neural Electrode for Precise Neural Modulation and Multi-Site Recording.

Applied Physics Express.

Glossary

Note 1: Optogenetics

Optogenetics is a technique to manipulate the activity of target neurons with light. This is achieved by gene transfer technology with which the illumination of light with specific wavelengths can express proteins that changes their activity. Channelrhodopsin-2, known as a typical protein, can introduce sodium ions into cells during neural activity when applying blue light and can artificially induce the activity of target neurons.