Lithographic patterning of conductive polyaniline

Electrically conducting patterns of polyaniline are made by utilizing conventional semiconductor industry process. First polyaniline is spin- or spray-coated on an insulating substrate and has a conductivity of 1–100 S/cm. After that UV resist is spread on top of polyaniline, exposed by UV light, developed and removed. As a result one has a patterned polyaniline layer in insulating and in conducting form on top of the substrate. The conductivity remains essentially unaffected below the resist throughout the process and polyaniline turns insulating at places where the resist is removed. The difference between the electrically conducting part and the electrically insulating part is upto 10¹⁰. When the linewidth is smaller than 100 μm the square resistance increases slightly, because the deprotonating liquid penetrates somewhat below the resist. Linewidths down to 10 μm have been demonstrated. The process has been utilized in making all-polymer circuit boards having resistors and capacitors made of polyaniline.