Electrical connectors for neural implants: design, state of the art and future challenges of an underestimated component

Abstract

Technological advances in electrically active implantable devices have increased the complexity of hardware design. In particular, the increasing number of stimulation and recording channels requires innovative approaches for connectors that interface electrodes with the implant circuitry. Objective. This work aims to provide a common theoretical ground for implantable connector development with a focus on neural applications. Approach. Aspects and experiences from several disciplines are compiled from an engineering perspective to discuss the state of the art of connector solutions. Whenever available, we also present general design guidelines. Main results. Degradation mechanisms, material stability and design rules in terms of biocompatibility and biostability are introduced. Considering contact physics, we address the design and characterization of the contact zone and review contaminants, wear and contact degradation. For high-channel counts and body-like environments, insulation can be even more crucial than the electrical connection itself. Therefore, we also introduce the requirements for electrical insulation to prevent signal loss and distortion and discuss its impact on the practical implementation. Significance. A final review is dedicated to the state of the art connector concepts, their mechanical setup, electrical performance and the interface to other implant components. We conclude with an outlook for possible approaches for the future generations of implants.

Neural signal recording and processing in somatic neuroprosthetic applications. A review

“…Significant improvements in materials, designs and fabrication procedures of implantable electrodes have been realized during the last two decades, overpassing the traditional, wafer-based integrated electronics (Patil and Thakor, 2016). To further improve the usability of the neural electrodes, considerable efforts are being devoted in the engineering field for increasing robustness and flexibility at the same time of miniaturizing the electrodes (Boehler et al, 2017;Won et al, 2018;Leber et al, 2019), improving the electrical connectors (Koch et al, 2019), and in the biological field to increase biocompatibility of the substrates and to modulate the foreign body reaction (Lotti et al, 2017;De la Oliva et al, 2019).…”

Soft Electronics Based on Stretchable and Conductive Nanocomposites for Biomedical Applications

“…[85] Moreover, neural recording with soft implantable electrodes has proven to be a powerful tool for researchers in the neuroscience field. [129,131,138] Despite the remarkable advances in implantable soft electronics, several challenges require further investigation in order to realize their full implementation in practical applications. A common obstacle for all fields using implantable soft electronics is their interface with rigid conventional electronics which are crucial for tasks such as data processing.…”

“…(B,ii) Reproduced with permission. [ 130 ] Copyright 2019, IOP Publishing. (C,i) Reproduced with permission.…”

“…Koch et al discuss the state of the art for electrical connectors for neural implants in great detail. [138] The second approach is implementing a wireless readout technology widely used for epidermal electronics. Wireless readout allows for a higher degree of freedom in animal experiments [129,139] as well as for humans.…”

Surgically Implanted Electrodes Enable Real-Time Finger and Grasp Pattern Recognition for Prosthetic Hands

“…The signal processing chain can readily be adapted to a low-power architecture ( 48 ), however many other system features need to be considered. Multi-channel percutaneous electrical connectors have been developed ( 49 ), but risks of complication and infection have limited their use to temporary or life-saving medical devices ( 50 ). Osseointegration is a hardware innovation that improves the mechanical linkage between user and prosthesis.…”