Implantable neural probes with monolithically-integrated micro-LEDs on silicon substrates have been demonstrated at the University of Michigan. Monitoring how neural circuits work together and perform computational processing is critical to the understanding of brain function and behavior. Through optogenetics, photosensitive ion channel proteins called opsins can be introduced into specific cell types to achieve optical control of defined action potential patterns in specific targeted neuronal populations. Neurons that express these opsins can be selectively stimulated by visible light at corresponding wavelengths with fast response times (milliseconds) and cell specificity, along with well-controlled spatial and temporal resolutions compared to conventional electrical stimulation methods. However, there remains an unmet need for reliable implantable tools that can precisely deliver light to targeted neurons and simultaneously record responses.
The technology developed at the University of Michigan solves the above challenge through integrated LED-on-silicon neural probes that demonstrate excellent barrier properties for reliability and are practical to build and implant. The technology allows for multiple cellular-scale GaN LEDs to be precisely aligned on the same probe shank with recording sites, obviating the need for hybrid processes to assemble components onto the probe shank. This, in turn, leads to increased scalability of the number of light sources per probe shank, minimized shank dimensions, and provides individual control of light sources for confined emission at sub-cellular resolution and multiple locations. The LED power supply can be wired to external electronics with flexible cables instead of the typically stiff optical fibers used in conventional optorode designs. The flexible cables enhance subject mobility due to reduced package size, rigidity, and mechanical coupling with the implanted probe. Additionally, the design supports easy wireless control.
Overall, due to the monolithic integration approach, the resulting micro-LEDs and electrodes can be designed with extremely small feature sizes (down to cellular dimensions) and high density (distance between micro-LED and electrode can be as small as 1 μm). Further, high-density arrays of light sources and recording electrodes can be freely configured into any spatial arrangement, and can aid studies of neural circuitries with very high spatial resolution.
- Neural circuits and interface systems
- Biomedical applications
- Monolithic fabrication process
- Excellent barrier properties and reliability
- Precise alignment of multiple cellular-scale LEDs
- Extremely small feature sizes (cellular dimensions)
- High density
- Confined stimulus delivery to multiple locations
- Extremely high resolution for single cell manipulation
- Higher subject mobility
- Reduced footprint
- Wireless control support