Yeager John D, Phillips Derrick J, Rector David M, Bahr David F
School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164, USA.
J Neurosci Methods. 2008 Aug 30;173(2):279-85. doi: 10.1016/j.jneumeth.2008.06.024. Epub 2008 Jul 3.
We developed a 64-channel flexible polyimide ECoG electrode array and characterized its performance for long-term implantation, chronic cortical recording and high resolution mapping of surface-evoked potentials in awake rats. To achieve the longest possible recording periods, the flexibility of the electrode array, adhesion between the metals and carrier substrate, and biocompatibility were critical for maintaining the signal integrity. Experimental testing of thin film adhesion was applied to a gold-polyimide system in order to characterize relative interfacial fracture energies for several different adhesion layers, yielding an increase in overall device reliability. We tested several different adhesion techniques including the following: gold alone without an adhesion layer, titanium-tungsten, tantalum and chromium. We found titanium-tungsten to be a suitable adhesion layer considering the biocompatibility requirements as well as stability and delamination resistance. While chromium and tantalum produced stronger gold adhesion, concerns over biocompatibility of these materials require further testing. We implanted the polyimide ECoG electrode arrays through a slit made in the skull of rats and recorded cortical surface evoked responses. The arrays performed reliably over a period of at least 100 days and signals compared well with traditional screw electrodes, with better high frequency response characteristics. Since the ultimate goal of chronically implanted electrode arrays is for neural prosthetic devices that need to last many decades, other adhesion layers that would prove safe for implantation may be tested in the same way in order to improve the device reliability.
我们开发了一种64通道的柔性聚酰亚胺脑皮层电图（ECoG）电极阵列，并对其在清醒大鼠中的长期植入、慢性皮层记录以及表面诱发电位的高分辨率映射方面的性能进行了表征。为了实现尽可能长的记录时间，电极阵列的柔韧性、金属与载体基板之间的粘附性以及生物相容性对于维持信号完整性至关重要。将薄膜粘附性的实验测试应用于金 - 聚酰亚胺系统，以表征几种不同粘附层的相对界面断裂能，从而提高整个器件的可靠性。我们测试了几种不同的粘附技术，包括：无粘附层的纯金、钛钨、钽和铬。考虑到生物相容性要求以及稳定性和抗分层性，我们发现钛钨是一种合适的粘附层。虽然铬和钽产生了更强的金粘附性，但对这些材料生物相容性的担忧需要进一步测试。我们通过在大鼠颅骨上制作的切口植入聚酰亚胺ECoG电极阵列，并记录皮层表面诱发反应。这些阵列在至少100天的时间内可靠运行，信号与传统螺丝电极相比良好，具有更好的高频响应特性。由于长期植入电极阵列的最终目标是用于需要持续数十年的神经假体装置，因此可以以相同的方式测试其他被证明对植入安全的粘附层，以提高器件的可靠性。
