Impact of Tip Size and Shape on the Insertion Force of Implantable CMOS Neural Probes

Tissue penetrating neural probes implementing high-density microelectrode arrays constitute a key tool of modern neuroscience. One of the main limitations of current probes to achieve chronically stable intracortical neural interfacing, is the biological reaction that they onset in the brain. Such foreign body reaction (FBR) is initiated by the mechanical tissue damage that the probes cause during their insertion, which is expected to be correlated with the force required to perform the implantation. One potential strategy to improve the integration of tissue penetrating high-density neural probes within brain tissue is to optimize their size and geometry in order to minimize acute tissue damage and Blood Brain Barrier (BBB) disruption. This strategy is foreseen to yield a more favorable postsurgical environment, reducing the extent of FBR in a chronic setting. In this context, the force required for the insertion of tissue penetrating neural probes can be used as an objective metric to assess the extent of acute tissue damage they induce. This paper reports preliminary findings on the impact of Complementary Metal Oxide Semiconductor (CMOS) probe geometrical parameters on insertion force, with a particular focus on the importance of tip size and shape on the dimpling of brain tissue before penetration.