Flexible High-Resolution Force and Dimpling Measurement System for Pia and Dura Penetration During In Vivo Microelectrode Insertion Into Rat Brain.

Understanding the in vivo force and tissue dimpling during micro-electrode implantation into the brain are important for neuro-electrophysiology to minimize damage while enabling accurate placement and stable chronic extracellular electrophysiological recordings. Prior studies were unable to measure the sub-mN forces exerted during in vivo insertion of small electrodes. Here, we have investigated the in vivo force and dimpling depth profiles during brain surface membrane rupture (including dura) in anesthetized rats. A µN-resolution cantilever beam-based measurement system was designed, built, and calibrated and adapted for in vivo use. A total of 244 in vivo insertion tests were conducted on 8 anesthetized rats with 121 through pia mater and 123 through dura and pia combined. Both microwire tip sharpening and diameter reduction reduced membrane rupture force (insertion force) and eased brain surface penetration. But dimpling depth and rupture force are not always strongly correlated. Multi-shank silicon probes showed smaller dimpling and rupture force per shank than single shank devices. A force measurement system with flexible range and µN-level resolution (up to 0.032 µN) was achieved and proved feasible. For both pia-only and dura-pia penetrations in anesthetized rats, the rupture force and membrane dimpling depth at rupture are linearly related to the microwire diameter. We have developed a new system with both µN-level resolution and capacity to be used in vivo for measurement of force profiles of various neural interfaces into the brain. This allows quantification of brain tissue cutting and provides design guidelines for optimal neural interfaces.

了解微电极植入大脑过程中的体内作用力和组织凹陷情况对于神经电生理学至关重要，这有助于在实现准确放置和稳定的慢性细胞外电生理记录的同时将损伤降至最低。先前的研究无法测量在体内插入小电极时所施加的亚毫牛级作用力。在此，我们研究了麻醉大鼠脑表面膜破裂（包括硬脑膜）过程中的体内作用力和凹陷深度曲线。 设计、构建并校准了一个基于微牛分辨率悬臂梁的测量系统，并使其适用于体内使用。在8只麻醉大鼠上共进行了244次体内插入测试，其中121次穿过软脑膜，123次同时穿过硬脑膜和软脑膜。 微丝尖端锐化和直径减小都降低了膜破裂力（插入力）并使脑表面穿透更容易。但是凹陷深度和破裂力并不总是高度相关。多针硅探针每个针的凹陷和破裂力比单针设备更小。 实现了一个具有灵活量程和微牛级分辨率（高达0.032微牛）的力测量系统，并证明是可行的。对于麻醉大鼠仅软脑膜穿透和硬脑膜 - 软脑膜穿透两种情况，破裂力和破裂时的膜凹陷深度都与微丝直径呈线性相关。 我们开发了一种新的系统，它具有微牛级分辨率并且能够在体内用于测量各种神经接口植入大脑的力曲线。这使得脑组织切割能够量化，并为优化神经接口提供了设计指南。