(I-359) Optimal Encapsulation for Neural Interface Devices: A Comparative Study of Polydimethylsiloxane and Bio-Epoxy

Introduction:: Thin-film intracortical microelectrode arrays have shown great promise in advancing the field of neural engineering. By enabling the recording and stimulation of neurons, these devices can give us a more intimate understanding of the brain than ever before. However, the long-term reliability of these devices remains a significant challenge, as previous studies have shown they often fail within an average of 387 days of use in non-human primate studies 1. The ability to stimulate neurons for 10+ years without failure is essential to the use of thin-film microelectrode arrays in a clinical setting. The purpose of this study was to determine the optimal packaging material and method for encapsulating neural interface devices.

Materials and Methods:: This study evaluated the effectiveness of two materials (bio-epoxy and polydimethylsiloxane) and two methods of encapsulation (overpour and casting) for insulating electrical components from the brain environment. Efficacy of packaging and electrical insulation was tested by performing long-term stress tests in phosphate buffered saline. Connectivity between electrode contacts within the packaging was quantified with electrochemical analysis via repeating chronoamperometry. The results of these trials showed that devices cast in polydimethylsiloxane after oxygen plasma pretreatment were able to insulate neural interface devices from the brain environment longer than cast or overpoured bio-epoxy, as characterized by the ultra-low connectivity (< 50 pA) between electrode contacts.

Results, Conclusions, and Discussions:: The final outcome is a packaging protocol for neural interface devices that has been proven to withstand high thermal and electrical stress tests; a more extreme environment than that found at typical operating conditions. Understanding the reasons for materials and packaging failure is crucial for the development of more reliable and robust microelectrode arrays. Casting neural interface devices in polydimethylsiloxane after oxygen plasma pretreatment has proven to successfully encapsulate devices with flexible substrates while maintaining desirable electrical insulation properties. The ability to encapsulate devices to maintain optimal function over years of continued use opens doors to further developments in neural interface devices such as increasing the resolution and specificity of neural signals, enhanced functionality of intracortical implants, and better adaptability of devices to specific patients, applications and new technologies. We have demonstrated the ability to safely package devices in a way that paves the road to new technological advancements that are not possible with current medical device encapsulation methods.


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Barrese JC, Rao N, Paroo K, et al. Failure mode analysis of silicon-based intracortical microelectrode arrays in non-human primates. J Neural Eng. 2013;10(6):066014. doi:10.1088/1741-2560/10/6/066014