Monolithic cathodes of optimized porosity prepared by sintering LiCoO2 powders provide high volume utilization and surprising stability under electrochemical cycling. Combined with a novel packaging approach, ultrahigh energy densities in small volumes are enabled. The microbatteries have volumes <6 mm3 and provide sustained ∼2.5 h discharges with energy densities of 400–650 W h L−1.

An implanted neural stimulator with closed loop control requires electrodes for stimulation pulses and recording neuron activity. Our system features arrays of 64 electrodes. Each electrode can be addressed through a cross bar switch, to enable it to be used for stimulation or recording. This electrode switch, a bank of low noise amplifiers with an integrated analog to digital converter, power conditioning electronics, and a communications and control gate array are co-located with the electrode array in a 14 millimeter diameter satellite package that is designed to be flush mounted in a skull burr hole. Our system features five satellite packages connected to a central hub processor-controller via ten conductor cables that terminate in a custom designed, miniaturized connector. The connector incorporates features of high reliability, military grade devices and utilizes three distinct seals to isolate the contacts from fluid permeation. The hub system is comprised of a connector header, hermetic electronics package, and rechargeable battery pack, which are mounted on and electrically interconnected by a flexible circuit board. The assembly is over molded with a compliant silicone rubber. The electronics package contains two antennas, a large coil, used for recharging the battery and a high bandwidth antenna that is used to download data and update software. The package is assembled from two machined alumina pieces, a flat base with brazed in, electrical feed through pins and a rectangular cover with rounded corners. Titanium seal rings are brazed onto these two pieces so that they can be sealed by laser welding. A third system antenna is incorporated in the flexible circuit board. It is used to communicate with an externally worn control package, which monitors the health of the system and allows both the user and clinician to control or modify various system function parameters.

Complex suture prostheses that deliver sensory and position feedback require a more sophisticated integration with the human user. Here a micro-size active implantable system that provides many-degree-of-freedom neural feedback in both sensory stimulation and motor control is shown, as one potential human-use solution in DARPA's HAPTIX program. Various electrical and mechanical challenge and solutions in meeting both sensory /motor performance as well as ISO 14708 FDA-acceptable human use in an aspirin-size active implementation are discussed.

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Deep brain stimulation therapies for Parkinson's disease utilize hardware that, from a packaging perspective, resembles those that are used in cardiac pacemakers. A hermetic package that contains stimulation electronics and a primary battery supply is implanted under the scalp into a recess formed in the skull. Stimulation probes, each with up to four electrodes, are inserted into the brain and connected to the electronics package via a plug and cable system. Unlike single-target devices such as cochlear implants and pacemakers, achieving this type of neuropsychiatric therapy requires the ability to record and stimulate in multiple and distributive areas of the brain, both cortical and subcortical. By contrast, the closed-loop neural stimulator being developed under the DARPA SUBNETS program utilizes probes, each of which carries up to 64 electrodes that can be switched between recording and stimulation functions. This capability necessitates locating low-noise amplifiers, switching and communication electronics in close proximity to each probe site. Each of these satellite electronics packages requires 10 electrical connections to the hub package, which significantly increases the complexity of the interconnect system relative to the current practice. The power requirements of this system preclude the use of a primary battery supply, so a large lithium ion battery is used, with a recharging coil and electronics. The hub system is composed of a connector header, electronics package, and battery pack that are fabricated separately and are interconnected by a flex circuit board, to allow it to conform to the skull for implanting. The standardized feedthrough substrate on the satellite, which can interface with multiple types of electrodes, along the system being reconfigurable, enables our architecture to support this new clinical research. It also allows the clinician to select satellite-electrode system based on a patient's needs, thus providing a customized, patient-specific therapeutic system. In this article, we have described the various packaging components of this system and the design considerations that drove our technology choices.