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    Neural Engineering

    In Vivo Implementation of Ultra-Microelectrode Arrays

    (K-407) In Vivo Implementation of Ultra-Microelectrode Arrays

    Friday, October 13, 2023
    9:30 AM – 10:30 AM PDT
    Location: Exhibit Hall - Row K - Poster # 407
    Introduction:: Microelectrodes are used to stimulate and record neural signals. However, a major challenge to chronic usage of microelectrodes in the brain is the foreign body response (FBR). Inflammatory cells encapsulate the devices, leading to the formation of a glial scar and increased impedance, thereby impairing long-term recording stability. To overcome these obstacles, we’ve begun the development of ultramicroelectrode arrays (UMEAs). UMEAs are specifically designed to be smaller than neuron somas, aiming to enhance biocompatibility and minimize the immune response, thus improving long-term recording stability. This study presents in vivo testing results of UMEAs, focusing on their effectiveness in microstimulation.

    Materials and Methods:: For our experimental setup, we used a custom 32-channel NeuroNexus UMEA with electrode diameters ranging from 5 µm to 50 µm. To improve charge storage capacity, the electrodes were coated in sputtered iridium oxide film (SIROF). The UMEA was implanted in the somatosensory cortex of anesthetized Sprague-Dawley rats weighing between 200 g and 400 g. Using the TDT RZ5D Bioamp Processor in conjunction with the TDT Subject Interface, we stimulated through multiple layers of the cortex. Our chosen stimulation method involved delivering cathodic leading, biphasic, charge-balanced square waves, with a phase width of 200 µs. The gathered data was recorded at 24 kHz, with local tissue serving as the reference. To collect the data, we used the software TDT Synapse. The neural activation data was filtered using Python 3.9.13, utilizing a Butterworth bandpass filter with a high-cut of 5000 Hz and a low-cut of 300 Hz.

    Results, Conclusions, and Discussions::

    We were able to record from individual neurons after running stimulation, demonstrating the functionality of the UMEAs. The gathered data shows a trend of recording quality changing with larger site size. These UMEAs show promise to be implanted in Sprague-Dawley rats for chronic experiments, to test the effectiveness in a long-term environment. Additionally, the success of this model has informed the development of a second generation model.




    With these encouraging results, we have taken a significant step towards overcoming the challenges of electrode degradation and immune response in neural implants. This opens up promising avenues for the development of long-lasting and biocompatible neural interfaces for future research and clinical applications.



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