Stretchable Low Impedance Electrodes for Bioelectronic Recording from Small Peripheral Nerves

Abstract

Monitoring of bioelectric signals in peripheral sympathetic nerves of small animal models is crucial to gain understanding of how the autonomic nervous system controls specific body functions related to disease states. Advances in minimally-invasive electrodes for such recordings in chronic conditions rely on electrode materials that show low-impedance ionic/electronic interfaces and elastic mechanical properties compliant with the soft and fragile nerve strands. Here we report a highly stretchable low-impedance electrode realized by microcracked gold films as metallic conductors covered with stretchable conducting polymer composite to facilitate ion-to-electron exchange. The conducting polymer composite based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) obtains its adhesive, low-impedance properties by controlling thickness, plasticizer content and deposition conditions. Atomic Force Microscopy measurements under strain show that the optimized conducting polymer coating is compliant with the micro-crack mechanics of the underlying Au-layer, necessary to absorb the tensile deformation when the electrodes are stretched. We demonstrate functionality of the stretchable electrodes by performing high quality recordings of renal sympathetic nerve activity under chronic conditions in rats.

Fully organic compliant dry electrodes self-adhesive to skin for long-term motion-robust epidermal biopotential monitoring

“…Although other stretchable PEDOT: PSS composites were used as the dry electrodes, they are not adhesive and thus give rise to high noise during body movement. Some soft adhesive electrodes were reported in literature 59,67 . For instance, ultrathin electrodes can be adhesive to skin.…”

Organic Bioelectronics: Using Highly Conjugated Polymers to Interface with Biomolecules, Cells, and Tissues in the Human Body

“…Pure conjugated polymer films can be brittle, tearing or cracking under strain. [ 26 ] Improving the mechanical properties of conjugated polymer systems has focused on developing either intrinsically stretchable polymers, [ 213–215 ] composites, [ 43,216–218 ] or conjugated polymer hydrogels. [ 39,219 ] Patterning materials with designs that compensate for motion are another approach, as developed for flexible thin film metal electrodes.…”

“…also demonstrated how polyethylene glycol could be incorporated into a PEDOT:PSS film during electropolymerization to tune the flexibility of a conductive interface used for chronic renal nerve recordings in a rat model ( Figure ). [ 216 ]…”

“…Adapted under the terms of CC‐BY 4.0 license. [ 216 ] Copyright 2019, The Authors, published by Springer Nature.…”

BMP-2 functionalized PEDOT:PSS-based OECTs for stem cell osteogenic differentiation monitoring

“…[18,21] Several devices have been developed based on this conducting polymer for a number of diverse applications embracing different fields such as tissue engineering, neural recording, neuromorphic computing, wearable and in vitro sensing. [22][23], [11], [24,25], [26][27][28] These materials hold promise for the electrical stimulation of osteogenic differentiation together with other electroactive materials and composite that have been explored for chronic electrical stimulation. [29,30] PEDOT:PSS-based organic electrochemical transistors (OECTs) are highly suited to sensing applications in aqueous environments, due to their ability to translate a biological event (e.g.…”