A Highly Stretchable and Conductive PEDOT:PSS/PEG-Coated Au Nanoparticle Nanomembrane for a Low-Impedance Biointerface

A biointerface, which denotes the interface between human biological systems and devices, plays an important role in the field of wearable and implantable electronics since mechanical mismatch leads to low signal-to-noise ratio, delamination of devices, and even tissue damage. However, achieving a conformal contact between the device and the tissue remains challenging due to its difficulty in simultaneously satisfying high stretchability, high conductivity, low impedance, and biocompatibility. Herein, we present a novel material of coating an Au nanoparticle nanomembrane (Au NP NM) with a mixture of polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) and polyethylene glycol (PEG) to fabricate a biointerface with ultrathin thickness, low impedance, high elasticity, and metal-like conductivity. Au NP NM, made of the float assembly with gold nanoparticles partially embedded on a styrene-ethylene-butylene-styrene (SEBS) substrate, forms a conductive percolation pathway that remains intact even in 200% tensile stretching. Then, the interaction between PEDOT:PSS/PEG and Au NP NM creates optimal contact, which improves the conductivity and durability while stretching (400%). Therefore, the coating of PEDOT:PSS/PEG does not disturb the Au percolation pathway rather, it reinforces its connectivity, thus improving stretchability, resulting in a biointerface with high charge storage capacity and high conductivity. This material could be incorporated into brain interfaces to facilitate efficient stimulation and monitoring of electrophysiological signals.