Fabrication and mechanical characterization of long and different penetrating length neural microelectrode arrays

Abstract

This paper presents a detailed description of the design, fabrication and mechanical characterization of 3D microelectrode arrays (MEA) that comprise high aspect-ratio shafts and different penetrating lengths of electrodes (from 3 mm to 4 mm). The array's design relies only on a bulk silicon substrate dicing saw technology. The encapsulation process is accomplished by a medical epoxy resin and platinum is used as the transduction layer between the probe and neural tissue. The probe's mechanical behaviour can significantly affect the neural tissue during implantation time. Thus, we measured the MEA maximum insertion force in an agar gel phantom and a porcine cadaver brain. Successful 3D MEA were produced with shafts of 3 mm, 3.5 mm and 4 mm in length. At a speed of 180 mm min −1 , the MEA show maximum penetrating forces per electrode of 2.65 mN and 12.5 mN for agar and brain tissue, respectively. A simple and reproducible fabrication method was demonstrated, capable of producing longer penetrating shafts than previously reported arrays using the same fabrication technology. Furthermore, shafts with sharp tips were achieved in the fabrication process simply by using a V-shaped blade.

Flexible deep brain neural probes based on a parylene tube structure

“…This number matches very well with the 11 mN penetration force through rat dura mater of sharpened silicon probes reported by Fekete et al [46]. Goncalves et al reported that the maximum insertion force of 180 µm wide silicon shank in 0.5% agarose gel is 2.65 mN and 12.5 mN in the porcine brain [47]. After passing this barrier, the insertion force dropped abruptly to 1.4 mN and then slowly increased to 2.0 mN when it stopped at a penetration depth of 11 mm.…”

Neural Interfaces for Intracortical Recording: Requirements, Fabrication Methods, and Characteristics

“…Nowadays glass insulation is used instead (Bhandari et al, 2009a ). Alternatively, electrodes can be electrically isolated and encapsulated within medical-grade epoxy resin removed from kerfs by dicing (Goncalves et al, 2015 ). In general, standard inorganic passivation layers are not sufficient to provide appropriate level of protection from body environment, thus supplementary encapsulation with polymers such as Parylene-C or polyimide is applied (Loeb et al, 1977 ; Hassler et al, 2011 ).…”

Determination of Stiffness and the Elastic Modulus of 3D-Printed Micropillars with Atomic Force Microscopy–Force Spectroscopy

“…The use of a scanning electron microscope is necessary to monitor the displacement in real-time during the mechanical test. Nanoindenters, tensile machines, or atomic force microscopes inside a scanning electron microscopy (SEM) chamber have been used to test tensile, compression, and bending of micropillars. − Although these approaches lead to reliable results, they require expensive and difficult-to-use instrumentation. For these reasons, some early experimental techniques with AFM that do not involve SEM have been proposed.…”