Abstract
Electrodes for interfacing implantable electronics and neural tissue are of great importance to gain a better understanding of the nervous system and to help people suffering from impaired body functions due to nerve lesions or lost organ functionality. In particular, neurostimulation techniques for bioelectronic medicine rely on the development of mechanically and electrochemically stable electrodes. While contemporary electrodes are based mainly on metals, new materials are being designed to enhance the mechanical and electrochemical properties of the interface. In this work, a nerve interface based on carbon nanotubes (CNTs) embedded in polydimethylsiloxane (PDMS) is fabricated and investigated. The fabrication process relies on the selective vacuum filtration of CNT suspensions through a printed wax pattern. The mechanical and electrochemical stability of the nerve interface was validated by 10 000 stretching cycles up to 20% strain and >4 × 106 biphasic stimulation pulses with 32 μC cm−2 per phase. The feedline resistance and electrode impedance showed only minor alterations after the stress tests. The functionality of the nerve interface was demonstrated by successful stimulation of the central nerve cord of a horse leech applying stimulation conditions within the water window of the CNT/PDMS electrodes. This work shows the practical usability of CNT/PDMS composites as electrodes and feedlines in peripheral nerve interfaces for future neuroprosthetic devices.
Highlights
Electrical stimulation of nerve and muscle tissue is a powerful tool for treating neurological disorders,[1] restoring impaired functionality,[2] and providing insight into understanding information processing in the nervous system.[3]
The fabrication relies on wax printing and vacuum filtration to pattern carbon nanotubes (CNTs) conductive feedlines and electrodes embedded into the surface of PDMS
We investigated the response of the CNT/PDMS
Summary
Electrical stimulation of nerve and muscle tissue is a powerful tool for treating neurological disorders,[1] restoring impaired functionality,[2] and providing insight into understanding information processing in the nervous system.[3] In this context, electrodes in direct contact or in close proximity to the target tissue are used as transceivers between the biologic and the electronic signal processing domains. The surface of metal electrodes is modified by inducing porosity[8] and oxide formation[9] or coating with carbon nanotubes (CNTs) and conducting polymers like poly(3,4-ethylenedioxythiophene).[10]. These surface alterations have the purpose to modify the electrochemical properties of bare metal electrodes in order to achieve a lower impedance and higher charge injection capacity (CIC). Higher currents can be injected into the tissue through the electrode without reaching potentials at the electrode–electrolyte interface that might cause damage to the tissue or the electrodes by irreversible electrochemical reactions.[11,12]
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