Amorphous Silicon Carbide Ultramicroelectrode Arrays for Neural Interfaces

    The clinical ability to record and stimulate neural activity with implanted microelectrode arrays has been limited by the problems of insertion trauma and foreign body response (FBR), which can lead to neuron damage and reduced reliability. Minimizing this tissue response is necessary for the development of implantable interfaces for studying neural activity and eventually treating chronic diseases.

    We present a multi-channel ultramicroelectrode (UME) array, comprised of amorphous silicon carbide (a-SiC) electrode shanks, that demonstrates effective neural recording and stimulation as an implanted neural interface. These a-SiC UME array devices are suitable for interfacing with both central and peripheral nerve systems, enabling the recording and stimulation of neural tissue with a spatial resolution not achievable with conventional microelectrodes currently used for the same purpose. In order to maximize biocompatibility, each shank is made entirely of a-SiC, which provides electrical insulation, electrode protection, and is extremely stable in the body, while also incorporating sufficiently-small cross-sectional dimensions that moderate or eliminate a FBR. Furthermore, the ultramicroelectrode dimensions of the a-SiC shanks imparts greater flexibility to the overall device while maintaining robustness, allowing it to bend without damage. While some of these features may be found in carbon-fiber electrodes, the simplified manufacturing process offered by this technology reduces the time needed to design and produce such devices drastically. A significant advantage of a-SiC UME arrays over carbon-fiber electrodes is that each a-SiC shank may have more than one individually-addressable electrode distributed along the length of the shank. Individual electrode shanks of the array may also be designed to splay in a divergent pattern to access a large volume of neural tissue. The additional features provided by the a-SiC UME arrays compared with carbon fiber UMEs, as well as their improved stability and reliability of neural recording, enables neural interfacing on a dimensional scale and spatial resolution not possible with current microelectrode recording technology.

Value Proposition:

    The presented a-SiC UME arrays enable the recording and stimulation of neural tissue with a spatial resolution unachievable with conventional microelectrodes used for the same purpose. These flexible, yet robust, devices are suitable for chronically-stable neural interfacing because they minimize insertion trauma by moderating, even eliminating the foreign body response – known to compromise the functionality of neural interfaces.

Figure 1: Optical micrographs show that the 16 shanks naturally bundle when the as-fabricated device is pulled out of the deionized water. Omnetics connectors were mounted on the arrays using a solder reflow process and medical grade epoxy. The figure shows (a) the as-fabricated a-SiC MEA after release from deionized water, (b) after an Omnetics connector is soldered onto the bond pads and (c) a packaged device for implantation or in vitro electrochemical characterization.

Applications:

• Microelectrode Arrays for Neural Research
• Neural Signal Collection and Recording with High Resolution
• Neural Stimulation with High Precision
• Biosensor Devices
• Bioelectronic Medicine
• Brain-Computer Interfaces
• Peripheral Nerve Interfaces

Key Benefits:

• Minimizes Injury – Shank dimensions minimize or avoid the foreign body response; materials exhibit excellent biocompatibility and stability in the body
• Scalable Manufacturing – Allows wafer-scale fabrication of a-SiC devices; design-to-manufacture time scales of a few weeks
• High-Yield and High-Resolution – Simultaneously records decoupled extracellular signals on all 16 channels of the arrays with very high spatial resolution; allows multiple recording sites per shank
• Reliable – Amorphous SiC effectively encapsulates conductive components of UMEs; maintains proximity to healthy neurons with extended implantation

Figure 2: A SEM image of the distal tip of an a-SiC UME shank with two electrode sites located on the same shank. The GSA of the exposed Au electrode sites is 100 μm² but with unequal perimeter. The perimeter of the square electrode site is 40 μm versus 104 μm for the rectangular site.

Publication:

Deku, Felix, et al. “Amorphous Silicon Carbide Ultramicroelectrode Arrays for Neural Stimulation and Recording.” Journal of Neural Engineering, vol. 15, no. 1, 8 Jan. 2018, doi:10.1088/1741-2552/aa8f8b.

IP Status: Patent pending.

Licensing Opportunity: This technology is available for exclusive or non-exclusive licensing.

ID Number: MP-17011

Contact: otc@utdallas.edu