Seaming the Bioelectronic Interface: Mechanisms, Strategies, and Validation Standards for Durable Poly(3,4-ethylenedioxythiophene)-Based Coating Adhesion.

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT)-based polymers have emerged as the unrivaled standards for mixed ionic-electronic conduction, bridging the gap between rigid electronics and soft biological tissues. However, the long-term operational stability of PEDOT-based devices is frequently compromised by a critical material failure: the delamination of the polymer coating under electrochemical and mechanical stress. This interfacial instability is a fundamental challenge shared across broad electrochemical applications, from bioelectronics to energy storage and fuel cells, where active materials undergo recurrent volumetric oscillation. While extensive research has optimized PEDOT-based polymers' electrochemical performance, the underlying interfacial mechanics remain insufficiently addressed in the literature. This review reconciles these disparate findings by first dissecting the genesis of the interface, illustrating how specific fabrication histories dictate fundamental failure modes: the intrinsic "stress accumulation" driven by <i>in situ</i> electropolymerization versus the osmotic "rehydration shock" characteristic of <i>ex situ</i> solution processing. Against this mechanistic backdrop, we establish a systematic framework for interfacial engineering, categorizing state-of-the-art adhesion strategies into two distinct paradigms: <i>Chemical Anchoring</i>, which leverages composites, intermediate layers, and functionalized derivatives to engineer covalent bridges; and <i>Physical Anchoring</i>, which utilizes "inside-out" deposition or "outside-in" etching to maximize mechanical interlocking. Beyond synthesis, we critically evaluate the lack of standardization in adhesion metrics, surveying techniques from <i>in vitro</i> stress tests to <i>in vivo</i> functional validation. By synthesizing these disparate methodologies, we propose a 3-tier benchmarking guideline to standardize future comparative studies. With these guidelines, we aim to outline a trans-disciplinary roadmap for seaming the biotic-abiotic divide, ensuring the reliability of the next-generation bioelectronic interface.