Patterning Polyacrylonitrile Thin Films Using Capillary Force Lithography

Polyacrylonitrile (PAN)-based conductive graphitic microstructures have tremendous potential for a variety of applications such as patterned electrodes, and anisotropic conductive films in the electronics industry because of its high carbonization yield. However, due to the crystallinity and high melting point of pristine PAN, thin films are difficult to get patterned at routine oven temperatures via methods such as capillary force lithography (CFL), a facile and low-cost lithographic technique. Herein, we demonstrate that simply adding a small amount of an ionic liquid (IL) can greatly improve the imprintability of PAN by decelerating the crystallization rate and providing PAN with the required mobility at accessible temperatures for efficient mold filling. The effect of IL additive concentration, annealing temperature and hold time on patterned PDMS mask on imprintability of PAN are well-correlated in a balancing act. The resulting patterned films demonstrate extraordinary IL removal ability at the end of the process, outstanding thermal stability of final patterned structures, and promising results on easy patterning route to fabricate graphitic microstructures after carbonization for a multitude of applications ranging from sensors to membranes.