Agarose Phantoms for Insertion Characterization of Amorphous SiC Microelectrode Probes in Rat Brain Tissue

Penetrating, Ultra-small Microelectrode Arrays (UMEAs) have been shown to evoke less foreign body response on implantation in neural tissue. This may be attributed to reduced tissue displacement on implantation and reduced mechanical mismatch between the highly flexible UMEA and tissue. However, the high flexibility of UMEAs makes implantation challenging. Establishing a robust model of tissue insertion may provide information on the forces encountered during implantation, assess the likelihood of UMEA penetration without buckling. In this study we measured insertion forces of amorphous SiC probes in rat cortex, and in 0.8 wt% and 1.2 wt% agarose models of brain tissue. The primary findings indicate that the 1.2% agarose model accurately predicts the maximum force of insertion obtained from measurements in rat. This suggests the suitability of the 1.2 wt% agarose model for the mechanical characterization of UMEAs prior to in vivo experimentation.