Long-term reliability of Al sub(2)O sub(3) and Parylene C bilayer encapsulated Utah electrode array based neural interfaces for chronic implantation

We focus on improving the long-term stability and functionality of neural interfaces for chronic implantation by using bi-layer encapsulation. Approach. We evaluated the long-term reliability of Utah electrode array (UEA) based neural interfaces encapsulated by 52 nm of atomic layer deposited Al2O3 and 6 mu m of Parylene C bi-layer, and compared these to devices with the baseline Parylene-only encapsulation. Three variants of arrays including wired, wireless, and active UEAs were used to evaluate this bi-layer encapsulation scheme, and were immersed in phosphate buffered saline (PBS) at 57[degrees]C for accelerated lifetime testing. The trends of increasing electrode impedance of wired devices and performance stability of wireless and active devices support the significantly greater encapsulation performance of this bi-layer encapsulation compared with Parylene-only encapsulation. The bi-layer encapsulation should significantly improve the in vivo lifetime of neural interfaces for chronic implantation.