(22) Development of a Host Module to Integrate Remote Sensors into a Neuroprosthesis Ecosystem

Introduction: The Networked Neuroprosthesis System (NNPS) is a modular, fully implanted system consisting of a central power module (PM) which provides power to and communicates with remote modules (RMs) including a pulse generator for neural stimulation and another to measure biopotential signal such as electromyography [1]. Current efforts are underway to make the system open-source and expand the system capabilities, as the platform architecture creates an opportunity for the development of additional modules that could easily be added to the existing system.

Methods: This project is developing a robust host module that can support a variety of analog and digital sensors by providing power supplies from 1.8-5V and multiple communication protocols (I2C, SPI, and UART) with the ability to switch between communication protocols and a built-in protocol for leak current detection. Our goal is to create a RM capable of interfacing with a variety of arbitrary outlying sensors, allowing for the streamlining of development and testing human grade implants and enabling placement of small sensors in distal appendages and on/between organs. Here we describe the packaging, circuitry, and software architecture of the SWARM module and sensor.

Results: RM circuitry is powered by a balanced AC waveform from the PM to that is rectified via RM circuitry; however, auxiliary sensors lack the space for rectification circuitry and will need to be powered using a transmitted DC current. To validate the header design for DC current delivery, an extended wear test was designed and performed; this test included resistance and leak current measurement in a saltwater bath to mimic a worst-case scenario. Testing revealed >100MΩ resistance between the ports and titanium can, as well as leakage currents < 2nA while driving 5mA DC while various strains were applied to the leads.

Conclusion: These results suggest that the current RM design is suitable for DC current applications.