Strong adhesion of wet conducting polymers on diverse substrates

Conducting polymers such as PEDOT:PSS, polypyrrole, and polyaniline are widely used as bioelectronic interfaces, but they often fail in wet environments due to weak adhesion and interfacial delamination. This study introduces a broadly applicable, fabrication-friendly adhesion strategy that enables robust bonding of wet conducting polymers to diverse insulating and conductive substrates (e.g., glass, polyimide, PDMS, ITO-glass, and gold). The approach adds a nanometer-thick hydrophilic polymer adhesive interlayer (demonstrated primarily with hydrophilic polyurethane, and also poly(vinyl alcohol) as an alternative) after substrate amine functionalization. The swollen hydrophilic interlayer allows conducting polymer precursors to diffuse into it, forming an interpenetrating polymer network while maintaining electrical contact to the underlying electrode. Using ASTM-style lap-shear testing in hydrated conditions, the method increased adhesion dramatically (e.g., PEDOT:PSS lap-shear strengths on amine-functionalized glass with PU reached ~160 kPa, compared with ~0.08 kPa on pristine glass without the interlayer) and shifted failure modes to cohesive failure within the conducting polymer. Electrical and electrochemical testing showed that a thin (nanometer-scale) adhesive layer preserves conductivity and maintains low interfacial resistance, while thicker (micron-scale) layers can increase impedance. The adhered conducting polymer coatings remained mechanically and electrochemically stable under harsh wet-condition challenges (including prolonged ultrasonication and extensive cycling), and the method enabled robust integration of conducting polymer coatings onto representative bioelectronic devices such as microelectrode arrays and microwire electrodes.