Comparative study on the insertion behavior of cerebral microprobes

Abstract

A series of experiments has been conducted with probes made from silicon, glass, tungsten and polyimide within a developed brain phantom, and the insertion behavior, forces and dimpling are compared to in vitro and in vivo models. This allows the choice of proper insertion parameters and probe structure to reach a compromise between needle stability and tissue trauma as a result of insertion. According to the performed experiments, the reduced interfacial area between the needle tip and the brain will result in reduced insertion force. High insertion speed (100 mm/min) reduces the dimpling but not the penetration force necessarily. In vivo insertion and retraction of the fragile probes made from silicon is possible without pia and/or dura removal.

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

“…Previous reports provided valuable statistical data on insertion mechanics of DRIE etched silicon shafts, however, like in previous experiments, layers of dura mater were removed before implantation [Welkenhuysen, 2011;Andrei, 2012]. The only preliminary data on probe penetration with intact and retracted dura is presented by Sharp et al (Sharp, 2009) and Hosseini et al (Hosseini, 2007), but no dependencies on geometry and implantation parameters were performed. Moreover, a systematic test on the effect of animal age was still not analyzed so far according to our knowledge.…”

“…Despite, only a few attempts have been made to thoroughly characterize single-shaft microprobes fabricated by DRIE technology from the point of view of in vivo insertion mechanics. Some groups compared single and multi-shaft individual silicon microelectrodes to microprobes fabricated from several materials [Jensen, 2006;Hosseini 2007]. Nevertheless, the fabrication of silicon probes is increasingly supported by deep reactive ion etching techniques [Spieth, 2011;, therefore investigating the feasibility of this microprobe technology is of great importance.…”

Chronic behavior evaluation of a micro-machined neural implant with optimized design based on an experimentally derived model

“…1 shows an example of such an insertion force measurement. As for similar literature studies [7], [8], four experimental outcome values were defined for each insertion experiment: the penetration force (F in ), its corresponding depth indicating the amount of dimpling (D in ), the end of the insertion force (F end ) and the sustained force value after 3 minutes tissue relaxation (F rest ). Only one probe was used for each rat, all implantations being performed in the ventromedial nucleus of the hypothalamus (VMH, coordinates: 3 mm posterior of bregma, 1 mm left to the mid-line and 9 mm ventral of the dura mater [13]).…”

“…Significant tissue deformation and blood vessel damage occurs during the implantation procedure itself [6]. The implant geometry and insertion speed have been shown to be closely related to this deformation [6], the insertion forces [7], [8], [9], [10] as well as to the acute and chronic tissue response [5], [2], [11]. However, most of these studies evaluated the contributions of only one or two parameters at a time, while fixing the rest.…”

Polymer-Based Approaches to Improve the Long Term Performance of Intracortical Neural Interfaces

“…In particular cases this is possible [23;24], but the insertion is limited to a certain depth and not easy to handle. A possibility to simplify the insertion is to bend the electrodes [25] to improve the stiffness but to have electrodes that are flexible enough to adapt to the mechanical conditions of the brain tissue. Takeuchi et al [26] used a parylene C based probe with integrated microfluidic channels, which were filled with polyethylene glycol (PEG) before insertion.…”