The aim of this proposal is to optimize the design and materials and to perform necessary pre-clinical testing of next-generation miniature, high-density multi-channel connectors suitable for chronic implantation in a patient's body. These `HD Connectors' will be part of systems that are used, for example, to treat disorders of the peripheral nervous system. Maladies that could be treated in this way are problems with walking, such as after a stroke, and restoring natural sensations in a phantom limb after amputation, among other examples. In this study, we will use custom-microfabricated, solid-filled connector bodies to facilitate interconnections within and among long-lasting neural interfaces. Custom encapsulation and assembly methods for the miniature connectors, developed with pilot funding, will be optimized. Under this proposal, we will fabricate variants of new HD connectors for mating with existing micro-neurostimulator designs. We will also evaluate the long-term biocompatibility and bio-stability of these connectors through both benchtop experiments and animal surgical trials. The data collected will then facilitate our application to the FDA to do follow-on clinical studies of medical devices incorporating this HD connector technology. The relationship between the proposed effort and the patient care mission of the VA is that these improvements are expected to increase the interchangeability of components of implantable neurostimulation systems for rehabilitation that have high channel counts. This will improve the safety and inter-operability of new devices under development, such as implantable walking aids and devices for restoring natural sensation in amputated limbs.