A highly conductive, biocompatible and stretchable sputtered Pt electrode via the island-bridge effect

Abstract

The development of stretchable electrodes is crucial for advancing soft electronics, including biointegrated health systems and wearable devices. In this work, we present a biocompatible and highly conductive stretchable hydrogel electrode fabricated by combining a conductive polymer (PEDOT:PSS) and a thin platinum layer (≈150 nm) deposited on top via radio frequency (RF) sputtering. The 2-hydroxyethyl acrylate (2-HEA) hydrogel acts as a flexible matrix into which the PEDOT:PSS polymer is incorporated, along with –OH groups that ensure strong adhesion of the metal layer to the hydrogel. The resulting electrode achieves a surface resistivity of 0.8 Ω sq⁻¹ (≈8 × 10⁶ S m⁻¹) and maintains conductivity even after 500 stretch–relaxation cycles at 70% strain. Unlike conventional electrodes, it exhibits minimal resistance variation (R/R₀ ≈ 2) under strain due to a combined “island-bridge” conduction mechanism. Importantly, the electrode preserves its conductivity even after one year of storage under ambient conditions. Additionally, under 40 °C and 70% RH for 48 h, the resistivity only shows a slight increase, which is recovered once returned to standard conditions. Furthermore, biocompatibility tests confirm the electrode's suitability for skin-contact applications. This novel approach provides a promising solution for next-generation wearable and implantable bioelectronics, offering an optimal balance between high conductivity, mechanical durability, stretchability and biocompatibility.