Comparison of Spray-Coating and Drop-Casting of PEDOT:PSS on Interdigitated Electrodes for Improved Interface Characteristics in Biosensors

Poly(3,4-ethylenedioxythiophene )-poly( styrene sulfonate) (PEDOT:PSS) is a conductive polymer yielding promising interface characteristics for biosensor electrodes. In this work, we compare two solution processing methods, namely drop-casting and spray-coating, for the deposition of PEDOT:PSS layers on gold interdigitated electrodes for electrical impedance spectroscopy based biosensing applications in fluid. Both techniques include (3-glycidyloxypropyl) trimethoxysilane (GOPS) as a crosslinker and reveal good stability in electrolytes. On the one hand, spray coating shows higher mechanical robustness, reproducibility, and better layer thickness control. On the other hand, drop-casting yields a 3-fold lower surface roughness and results in improved double-layer characteristics with a capacitance of 157 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{F}$</tex> compared to 3 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{F}$</tex> of bare gold. Both deposition techniques promise higher electrode reproducibility and improved interface characteristics, especially in the lower frequency range.