High Density, Double-Sided, Flexible Optoelectronic Neural Probes With Embedded μLEDs

Area of Science:

• Neuroscience
• Materials Science
• Biomedical Engineering

Background:

• Optical stimulation and recording of neural circuits deep within the brain are crucial for understanding brain function and developing new therapies.
• Current implantable optical probes face limitations due to light scattering and absorption in tissues, and rigid materials can cause significant tissue damage.
• Flexible probes offer a promising alternative for chronic neural interfacing, reducing tissue trauma and enabling long-term studies.

Purpose of the Study:

• To develop a monolithic, wafer-scale microfabrication process for flexible optoelectronic neural probes with embedded gallium nitride micro-light-emitting diodes (μLEDs).
• To create individually-addressable μLED arrays on flexible substrates for precise optical stimulation of neural tissue.
• To integrate recording electrodes for simultaneous electrophysiology and bi-directional optical stimulation.

Main Methods:

• Microfabrication of gallium nitride (GaN) μLEDs on a flexible Parylene C substrate.
• Development of one-dimensional and two-dimensional individually-addressable μLED arrays.
• Co-fabrication of recording electrodes on both sides of the flexible probes.

Main Results:

• Demonstrated wafer-scale fabrication of flexible μLED neural probes with μLEDs as small as 22 × 22 μm.
• Achieved blue light emission (445 nm) with output power >200 μW at 2 mA, suitable for channelrhodopsin-2 stimulation.
• Developed double-sided probes capable of simultaneous optical stimulation and electrophysiology recording from both sides of the tissue.

Conclusions:

• The developed monolithic flexible μLED neural probes offer a biocompatible and minimally invasive solution for advanced neural interfacing.
• Wafer-scale fabrication enables scalable production of these high-performance optoelectronic probes.
• The ability to perform simultaneous bi-directional optical stimulation and neural recording opens new avenues for closed-loop brain circuit manipulation and research.