Amphiphilic Silicones for the Facile Dispersion of Carbon Nanotubes and Formation of Soft Skin Electrodes

Abstract

Flexible, dry skin electrodes represent a potentially superior alternative to standard Ag/AgCl metal electrodes for wearable devices used in long-term monitoring. Herein, such electrodes were formed using a facile method for dispersing carbon nanotubes (CNTs) in a silicone matrix using custom amphiphilic dispersive additives (DSPAs). Using only brief mixing and without the use of solvents or surface modification of CNTs, 12 poly(ethylene oxide)-silanes (PEO-SAs) of varying cross-linkability, architecture, siloxane tether length, and molar ratio of siloxane:PEO were combined with an addition cure silicone and CNTs. Nearly all PEO-SA-modified silicone−CNT composites demonstrated improved conductivity compared to the unmodified composite. The best conductivities correlated to composites prepared with PEO-SAs that formed micelles of particular sizes (d of ∼ 200−300 nm) and coincided to PEO-SAs with a siloxane:PEO molar ratio of ∼0.75−3.00. Superior dispersion of CNTs by such PEO-SAs was exemplified by scanning electron microscopy. Advantageously, modified composites retained their moduli, rather than becoming more rigid. Resultant electrodes fabricated with modified composites showed skin-electrode impedance comparable to that of Ag/AgCl electrodes. Combined, these results demonstrate the potential of silicone−CNT composites prepared with PEO-SA DSPAs as flexible, dry electrodes as a superior alternative to traditional electrodes.

Biomedical Silicones: Leveraging Additive Strategies to Propel Modern Utility

“…Nonetheless, this required a pretreatment to impart negative charges at the surface of the CNTs to ensure proper adhesion with the positively charged SDS. Our group has focused on the creation and use of a PEO-silane DSPA, which would allow for simple CNT separation . DSPA architecture (linear and star) and siloxane length were systematically varied to investigate their impact on CNT dispersion.…”

“…Our group has focused on the creation and use of a PEO-silane DSPA, which would allow for simple CNT separation. 166 DSPA architecture (linear and star) and siloxane length were systematically varied to investigate their impact on CNT dispersion. These were combined with CNTs and an addition cure silicone, without modification to CNTs, addition of solvents, or exhaustive mixing protocols.…”