Experimental study on the mechanical interaction between silicon neural microprobes and rat dura mater during insertion

Abstract

In vivo insertion experiments are essential to optimize novel neural implants. Our work focuses on the interaction between intact dura mater of rats and as-fabricated single-shaft silicon microprobes realized by deep reactive ion etching.Implantation parameters like penetration force and dimpling through intact dura mater were studied as a function of insertion speed, microprobe cross-section, tip angle and animal age. To reduce tissue resistance, we proposed a unique sharpening technique, which was also evaluated through in vivo insertion tests.By doubling the insertion speed (between 1.2 and 10.5 mm per minute), an increase of 10-35 % in penetration forces was measured. When decreasing the cross-section of the microprobes, penetration forces and dimpling can be reduced by as much as 30-50 % at constant insertion speeds. Force is gradually deceasing by decreasing tip angles. Measured penetration forces through dura mater were reduced even down to 11 ± 3 mN compared to unsharpened (49 ± 13 mN) probes by utilizing our unique probe sharpening technique, which is very close to exerted penetration force in the case of retracted dura (5 ± 1.5 mN).Our findings imply that age remarkably alters the elasticity of intact dura mater. The decreasing stiffness of dura mater results in a significant rise in penetration force and decrease in dimpling.Our work is the first in vivo comparative study on microelectrode penetration through intact and retracted dura mater.

A microfabricated, 3D-sharpened silicon shuttle for insertion of flexible electrode arrays through dura mater into brain

“…Due to the deformable nature of the brain, the boundary condition on the brain side is not completely translation fixed, with true n less than 2 and true Fcrit expected to be slightly lower than calculated. Our maximum insertion force for transdural insertion of sharpened shuttles of aproximately 10 mN is lower than previous reports for planar devices (e.g., 41 mN with silicon probes; Hosseini et al, 2007) and similar to the 11 ± 2 mN reported previously in a proof-of-concept study in which a less flexible, silicon-specific etch technique was used to insert but not record from silicon probes (Fekete et al, 2015). For comparison, previously reported peak insertion forces for rat pia-only insertions are approximately 5 mN (Paralikar andClement*, 2008, Fekete et al, 2015).…”

“…Previous work has demonstrated the benefits of sharpened device tips in reducing insertion force (Sharp et al, 2009, Fekete et al, 2015, Obaid et al, 2018 and penetrating dura (Hosseini et al, 2007, Fekete et al, 2015, Sharp et al, 2009. Here, we sharpen not only in two dimensions but three, resulting in a more gradually increasing cross-section (Chen et al, 2017, Fekete et al, 2015.…”

“…Another way to reduce brain compression could be to change insertion speed. A range of speeds, including meters-per-second scale pneumatic insertion (Black et al, 2018), have yielded dural penetration (Fekete et al, 2015) and neural recordings (Zhao et al, 2019, Hosseini et al, 2007, P. Rousche, 1992, with the optimal speed dependent on tip shape and features in the target tissue, such as vessels (Bjornsson et al, 2006). Retraction speed, too, has been varied; for example, the ballistic retraction method used in combination with needle-and-thread insertion to prevent displacement of electrodes from target depth has, as previously discussed, yielded chronic neural recordings (Hanson et al, 2019).…”

CHIME: CMOS-hosted in-vivo microelectrodes for massively scalable neuronal recordings

“…This causes problems if the maximal force is below the force needed for insertion. Measurements have been made for different types of electrodes (Sharp et al, 2009;Casanova et al, 2014;Fekete et al, 2015), and recently a quantitative study was undertaken to understand the penetration mechanics of microwires specifically (Obaid et al, 2018). In our experiments, 15-20 μm wires could be inserted into the cortex several millimetres deep without support.…”

Headers and Payloads Inside of Nervous System as Like as Digital Communication Protocols ?

“…The recording capabilities may be affected by biocompatibility with the patient [22], [23] y [24], traumatic nerve damage at electrode insertion [25], a bad mechanical adjustment due to the rigid electrode structure [26], tissue softness [27], non-penetration to fascicle [28], and the forces by the immobilization of the transcutaneous connection cables have been subjects treated in many publications in the last years [29], [30] y [31].…”