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(7) A Comparison in Implanting Flexible Microelectrode Arrays Across Multiple Animal Models

Friday, June 13, 2025
5:50 PM - 6:30 PM ET
Location: Sky View
Introduction: Implantable flexible microelectrode arrays for electrophysiology have been crucial tools to enable the neuroscience community to track single units over the course of days, weeks, and months (1). As usage of these tools has expanded into numerous animal models, it has become apparent that the surgical approach and design considerations must be tailored to each animal model. Here, we compare and contrast the engineering approaches that have gone into enabling flexible microelectrode arrays to be implanted in rodent, songbird, and nonhuman primate (NHP) models.

Methods: Multielectrode arrays were fabricated using microfabrication techniques in a variety of designs, varying dimensions such as electrode size, electrode spacing, shank length, and shank number to suit varying animal models. These arrays comprise of polyimide substrate and platinum microelectrodes, onto which PEDOT:PSS was electroplated to reduce electrochemical impedance and increase sensitivity to single unit recordings. To enable implantation of the array into the brain to a desired depth, silicon surgical insertion shanks were fabricated to be temporarily attached to the interface, stiffening the shank such that the array can be implanted. The tips of these shanks are patterned in a 3D fashion to reduce insertion force onto the tissue during surgery (2).

Results: As surgical shanks were fabricated and tested among each animal model, it was found that engineering modifications were required to enable implantation of longer shanks, such as those required for NHP. While rodent models could be implanted to 8 millimeter depths with 30 micrometer-thick surgical shanks, NHP models that necessitated 40 millimeter insertion depths required surgical shanks that were 200 micrometers thick. Thinner insertion shanks led to buckling of the shank during surgery. Fine tuning these parameters has enabled surgical placement of these arrays into each animal model and demonstrated implant lifetimes of weeks to months. We have also found differences in surgical technique required for longer term recordings in similarly-sized brains, such as the implant procedure in rodents compared to songbirds.

Conclusion: As microfabrication techniques for neural interfaces advance and enable higher channel count recordings in smaller physical footprints, these findings can help dictate optimal surgical insertion approaches to provide long-lasting electrophysiological recordings for a variety of animal models. Considering these results will help establish best practices for future success as the use of neural interfaces expands to new animal models.