Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States of America.
Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, United States of America.
J Neural Eng. 2024 Aug 14;21(4). doi: 10.1088/1741-2552/ad68a6.
Implanted neural microelectrodes are an important tool for recording from and stimulating the cerebral cortex. The performance of chronically implanted devices, however, is often hindered by the development of a reactive tissue response. Previous computational models have investigated brain strain from micromotions of neural electrodes after they have been inserted, to investigate design parameters that might minimize triggers to the reactive tissue response. However, these models ignore tissue damage created during device insertion, an important contributing factor to the severity of inflammation. The objective of this study was to evaluate the effect of electrode geometry, insertion speed, and surface friction on brain tissue strain during insertion.. Using a coupled Eulerian-Lagrangian approach, we developed a 3D finite element model (FEM) that simulates the dynamic insertion of a neural microelectrode in brain tissue. Geometry was varied to investigate tip bluntness, cross-sectional shape, and shank thickness. Insertion velocities were varied from 1 to 8 m s. Friction was varied from frictionless to 0.4. Tissue strain and potential microvasculature hemorrhage radius were evaluated for brain regions along the electrode shank and near its tip.. Sharper tips resulted in higher mean max principal strains near the tip except for the bluntest tip on the square cross-section electrode, which exhibited high compressive strain values due to stress concentrations at the corners. The potential vascular damage radius around the electrode was primarily a function of the shank diameter, with smaller shank diameters resulting in smaller distributions of radial strain around the electrode. However, the square shank interaction with the tip taper length caused unique strain distributions that increased the damage radius in some cases. Faster insertion velocities created more strain near the tip but less strain along the shank. Increased friction between the brain and electrode created more strain near the electrode tip and along the shank, but frictionless interactions resulted in increased tearing of brain tissue near the tip.. These results demonstrate the first dynamic FEM study of neural electrode insertion, identifying design factors that can reduce tissue strain and potentially mitigate initial reactive tissue responses due to traumatic microelectrode array insertion.
植入式神经微电极是记录和刺激大脑皮层的重要工具。然而，慢性植入设备的性能常常受到反应性组织反应的发展的阻碍。以前的计算模型已经研究了神经电极插入后的微运动引起的大脑应变，以研究可能最小化引发反应性组织反应的设计参数。然而，这些模型忽略了在器械插入过程中造成的组织损伤，这是炎症严重程度的一个重要因素。本研究的目的是评估电极几何形状、插入速度和表面摩擦对插入过程中脑组织应变的影响。使用偶联的欧拉-拉格朗日方法，我们开发了一个 3D 有限元模型 (FEM)，模拟神经微电极在脑组织中的动态插入。改变几何形状以研究尖端钝度、横截面形状和柄部厚度。插入速度从 1 到 8 m s 不等。摩擦从无摩擦到 0.4 不等。评估了沿着电极柄部和靠近其尖端的脑组织区域的应变和潜在微血管出血半径。除了方形横截面电极上最钝的尖端由于拐角处的应力集中导致高压缩应变值外，较锋利的尖端在尖端附近产生较高的平均最大主应变。电极周围的潜在血管损伤半径主要取决于柄部直径，较小的柄部直径导致电极周围的径向应变分布较小。然而，方形柄部与尖端锥度长度的相互作用导致了一些情况下增加的应变分布，从而增加了损伤半径。较快的插入速度在尖端附近产生更多的应变，但在柄部上产生较少的应变。电极和大脑之间的摩擦增加会在电极尖端和柄部附近产生更多的应变，但无摩擦相互作用会导致尖端附近脑组织的撕裂增加。这些结果表明了神经电极插入的第一个动态 FEM 研究，确定了可以减少组织应变并可能减轻由于创伤性微电极阵列插入引起的初始反应性组织反应的设计因素。
