Soft peripheral nerve interface made from carbon nanotubes embedded in silicone

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.

Wearable Sensors for Healthcare: Fabrication to Application

“…The sensors could operate with a frequency shift up to a maximum limit of 20 mm and 10 mm in air and phantom, respectively. CNTs have also been considered to develop wearable neural sensors, as reported in [ 152 ]. Soft peripheral nerve interfaces were made from CNTs embedded in silicone polymers.…”

Exploring polymeric biomaterials in developing neural prostheses

“…PDMS is a well-known polymer that is often used for biomedical applications especially for electrode fabrication or insulation. 23,35 It is usually used as a substrate insulating electrodes, meaning the area which it is exposed to tissues are relatively greater than that of electrodes. It is vital to take note of the hydrophobic and low lubric nature of PDMS as they have the tendency to increase the chances of protein adsorption and insertion trauma, respectively.…”

“…Good electrical conductivity, large surface area, good mechanical strength Terkan et al, 23 Eleftheriou et al, 24 Ostrovsky et al, 25 Lu et al 26…”

Soft Implantable Bioelectronics

“…Intrinsically soft and stretchable electrodes have been designed to possess mechanical properties similar to those of the peripheral nerves. − In addition to the soft and stretchable properties, it is necessary to have stable and excellent electrical conduction properties for localized electrical stimulation of the nerves. Hydrogels are a promising candidate for soft neural electrode materials; however, their low conductivity and difficulty in micropatterning have been a bottleneck for their application in soft implantable bioelectronics.…”