A Waterborne, Flexible, and Highly Conductive Silver Ink for Ultra-Rapid Fabrication of Epidermal Electronics

Epidermal electronics provide a promising solution to key challenges in wearable electronics, such as motion artifacts and low signal-to-noise ratios caused by an imperfect sensor-skin interface. To achieve the optimal performance, skin-worn electronics require high conductivity, flexibility, stability, and biocompatibility. Herein, we present a nontoxic, waterborne conductive ink made of silver and child-safe slime for the fabrication of skin-compatible electronics. The ink formulation includes polyvinyl acetate (PVAc), known as school glue, as a matrix, glyceryl triacetate (GTA) as a plasticizer, sodium tetraborate (Borax) as a crosslinker, and silver (Ag) flakes as the conducting material. Substituting citric acid (CA) for GTA enhances the deformability by more than 100%. With exceptional conductivity (up to 1.17 × 10⁴ S/cm), we demonstrate the ink's potential in applications such as an epidermal near-field communication (NFC) antenna patch and a wireless ECG system for motion monitoring.