# Profiled Wet Spinning of Polyurethane Composites for Soft Dry Electrodes in Transcutaneous Stimulation Applications

## TL;DR

This paper introduces soft, dry electrodes made using wet spinning techniques for comfortable and effective nerve stimulation through the ear.

## Contribution

The study presents two novel fabrication methods for soft dry electrodes using polyurethane composites suitable for taVNS.

## Key findings

- The wet-spun electrodes show high conductivity and mechanical resilience under strain and compression.
- The hollow cylindrical electrodes maintain low material impedance even in dry conditions.
- Bench and human testing confirmed the electrodes' performance for transcutaneous stimulation applications.

## Abstract

Transcutaneous electrical nerve stimulation techniques (TENS) are rapidly gaining attention for their potential in various clinical applications. One such technique is transcutaneous auricular vagus nerve stimulation (taVNS), and it involves delivering nerve stimulation through the skin of the external ear. However, taVNS relies on electrodes that must conform to the complex anatomy of the ear while maintaining stable electrical performance. Conventional taVNS electrodes, typically rigid metal or adhesive pads, are uncomfortable, difficult to position, prone to drying, and costly to produce. Here, we present and evaluate two complementary fabrication approaches for soft dry electrodes suitable for taVNS, which are compliant with curved anatomical features and can be operated without gel. The first employs wet spinning of a conductive elastomer into fibers, while the second extends this method to create hollow cylindrical geometries. The resulting spongy polymer composite electrodes exhibit tunable geometry, high conductivity, mechanical resilience under strain and compression, and low material impedance confirmed through bench and human testing, even under dry conditions. These properties are critical for in-ear and broader transcutaneous stimulation applications, highlighting the potential of these fabrication methods for next-generation soft bioelectronic interfaces.