ARISE Scholar: Ariba Chowdhury
Mechanical Characterization of Microelectrodes: Used for Auditory Cortical Prostheses
We investigated the mechanics of the forces within the junction of polyimide insulated stainless steel microelectrode (diameter= 125 um) and auditory cortical interfaces of rat and human brain tissue (1mm and 3.5 mm, respectively). Insertions were performed on formalin fixed human brain (FHB) tissue (10 % formaldehyde) at 5 mm increments from anterior to posterior HG. In formalin fixed rat brain (FRB) (10% formaldehyde) and non formalin fixed rat brain (NRB) tissue, insertions were made at 2mm increments from anterior to posterior hemisphere. The forces of insertion, steady state, and retraction of the electrode were measured by a SMD Sensors 500 mN thin film strain gage load cell which was mounted on a three-dimensional micromanipulator. Insertion force showed highest resistive behavior at magnitudes of 8.584 mN for NRB, 18.181 mN for FHB and 39.453 mN for FRB, signifying viscoelastic characteristic of cortical tissue. Force peaks corresponding to NRB tissue were significantly lower (by a factor of 3 for penetration and steady state, 2 for retraction forces) than FRB tissue, suggesting less force requirement and more pliable in live brain tissue. Upon retraction, the force experienced by the electrode suggests the tensile characteristic of cortical tissue.