Flexible Gold Electrodes with Enhanced Adhesion and Electrochemical Performance via Silane-Modified PDMS for Bioelectronics

Abstract

Achieving strong adhesion and stable electrical performance of conductive films on soft polymer substrates remains a key challenge in developing flexible bioelectronic devices. In this work, a surface modification strategy is introduced for polydimethylsiloxane (PDMS) that allows for the formation of gold pathways with robust adhesion and desirable electrical interface properties. The PDMS surface is chemically activated with oxygen plasma and functionalized with 3-mercaptopropyltrimethoxysilane, enabling covalent bonding to the deposited gold layer. Surface characterization confirms uniform gold coverage and the presence of sulfur from thiol-terminated silane groups, while Fourier-transform infrared spectroscopy verifies successful chemical grafting. Adhesion tests under wet conditions demonstrate the excellent durability, withstanding immersion and ultrasonication without delamination. A 130 nm gold layer provides optimal properties, including a low sheet resistance (≈15 Ω sq−1). Electrochemical analysis shows a double-layer capacitance of ∼24 µF·cm−2 and a charge storage capacity of 495 ± 48 µC·cm−2 at 200 mV·s−1, representing ∼67% of the performance of commercial platinum. Notably, the current injection limit reached 8 mA, over twice that of platinum, without exceeding the safe potential window. This silanization protocol enables scalable integration of flexible, electrochemically robust gold traces on PDMS for next-generation neural interfaces and soft bioelectronic systems.