PROJECT TITLE :

Parylene-Based Electrochemical-MEMS Force Sensor for Studies of Intracortical Probe Insertion Mechanics

ABSTRACT:

To investigate the mechanical interactions between the implanted cortical multielectrode probes and brain tissue, a Parylene C-based electrochemical-microelectromechanical systems force sensor array was developed. The array consists of seven linearly distributed sensor units arranged along the length of a flexible Parylene C microchannel. The seven sensor units are formed by eight fluidically coupled and adjacent platinum electrode pairs enclosed inside the microchannel. Deformation of the prime surface of the mechanically compliant microchannel changes the volumetric conduction path between the pairs of sensing electrodes, and thus, the measured electrochemical impedance, which is proportional to the magnitude of the contacting force. Every sensor unit demonstrated a linear response from zero to 60 mN with a sensitivity of 0.thirteen ± 0.01 percentage modification in impedance/μN (%/μN; mean ± SE, n = half-dozen). The sensor arrays were mounted onto a ceramic intracortical probe and inserted into the tissue phantoms to verify in situ functionality and assess interfacial probe mechanics. Probe surface force distribution was measured below various insertion speeds and therefore the results indicated that interfacial forces are distributed nonuniformly along the probe shaft length, concentrating within the first 1 mm of the advancing probe tip. Faster insertion speeds were conjointly found to decrease the magnitude of the interfacial forces, suggesting that the tissue strain during cortical implantation might be minimized through applicable choice of the insertion speed.