All-polymer free-standing electrodes for flexible electrochemical sensors

Flexible free-standing electrodes with inherent conductivity and superior mechanical property are highly desired for flexible electrochemical sensor. Herein, we report the design of all-polymer flexible film electrodes for dopamine (DA) detection, in which polypyrrole (PPy) doped with pentaerythritol ethoxylate (PEE) are grown together with PPy doped with 2-naphthalene sulfonate (2-NS-PPy) by adopting sandwiched structure. This all-polymer electrode is free-standing and breaks through the bottleneck of traditional flexible electrodes that requires elastic substrate and conductive additives, demonstrating high mechanical tensile strength (81.9 MPa), good flexibility (elongation-at-break of 41.6 %), and inherent and stable conductivity. When used as electrochemical sensor for DA detection, this PPy composite film electrode shows high sensitivity (343.75 mu A mM(-1) cm(-2)). Moreover, this all-polymer electrode can bear various deformation (bending, twisting, folding, and knotting) with negligible effect on the sensing performance. This electrochemical sensor demonstrates strong electrochemical stability with 97.3 % current response remaining at 25 % strain for DA detection. The strong sensing stability (mechanical deformation and long-time storage), in conjunction with superior mechanical property and high sensitivity, proves that this all-polymer free-standing film electrode exhibits giant potential in application of flexible electrochemical sensors.