Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75080, United States of America.
J Neural Eng. 2018 Feb;15(1):016007. doi: 10.1088/1741-2552/aa8f8b.
Foreign body response to indwelling cortical microelectrodes limits the reliability of neural stimulation and recording, particularly for extended chronic applications in behaving animals. The extent to which this response compromises the chronic stability of neural devices depends on many factors including the materials used in the electrode construction, the size, and geometry of the indwelling structure. Here, we report on the development of microelectrode arrays (MEAs) based on amorphous silicon carbide (a-SiC).
This technology utilizes a-SiC for its chronic stability and employs semiconductor manufacturing processes to create MEAs with small shank dimensions. The a-SiC films were deposited by plasma enhanced chemical vapor deposition and patterned by thin-film photolithographic techniques. To improve stimulation and recording capabilities with small contact areas, we investigated low impedance coatings on the electrode sites. The assembled devices were characterized in phosphate buffered saline for their electrochemical properties.
MEAs utilizing a-SiC as both the primary structural element and encapsulation were fabricated successfully. These a-SiC MEAs had 16 penetrating shanks. Each shank has a cross-sectional area less than 60 µm and electrode sites with a geometric surface area varying from 20 to 200 µm. Electrode coatings of TiN and SIROF reduced 1 kHz electrode impedance to less than 100 kΩ from ~2.8 MΩ for 100 µm Au electrode sites and increased the charge injection capacities to values greater than 3 mC cm. Finally, we demonstrated functionality by recording neural activity from basal ganglia nucleus of Zebra Finches and motor cortex of rat.
The a-SiC MEAs provide a significant advancement in the development of microelectrodes that over the years has relied on silicon platforms for device manufacture. These flexible a-SiC MEAs have the potential for decreased tissue damage and reduced foreign body response. The technique is promising and has potential for clinical translation and large scale manufacturing.
驻留皮质微电极的异物反应限制了神经刺激和记录的可靠性，尤其是对于行为动物的扩展慢性应用。这种反应对神经设备慢性稳定性的影响取决于许多因素，包括电极结构中使用的材料、驻留结构的大小和几何形状。在这里，我们报告了基于非晶硅碳化硅 (a-SiC) 的微电极阵列 (MEA) 的开发。
这项技术利用 a-SiC 的慢性稳定性，并采用半导体制造工艺来制造具有小柄尺寸的 MEA。a-SiC 薄膜通过等离子体增强化学气相沉积沉积，并通过薄膜光刻技术进行图案化。为了提高小接触面积的刺激和记录能力，我们研究了电极部位的低阻抗涂层。组装后的器件在磷酸盐缓冲盐中进行电化学特性表征。
成功制造了同时使用 a-SiC 作为主要结构元件和封装的 MEA。这些 a-SiC MEA 有 16 个穿透柄。每个柄的横截面积小于 60 µm，电极部位的几何表面积从 20 到 200 µm 不等。TiN 和 SIROF 电极涂层将 1 kHz 电极阻抗从 100 µm Au 电极部位的约 2.8 MΩ降低到小于 100 kΩ，并将电荷注入容量增加到大于 3 mC cm 的值。最后，我们通过记录斑马雀基底神经节核和大鼠运动皮层的神经活动证明了功能。
a-SiC MEA 在微电极的开发方面取得了重大进展，多年来，微电极的开发一直依赖于硅平台进行器件制造。这些柔性 a-SiC MEA 具有降低组织损伤和减少异物反应的潜力。该技术很有前途，具有临床转化和大规模制造的潜力。
