ABSTRACT
When a thin polymer film supported by a conductive substrate is contacted by and then separated from a micropatterned polymeric stamp, the so-called contact electrification creates electrical charges over the stamped regions. Simultaneously, image charges are induced in the conductive substrate. Together, the surface and image charges establish large fields within the film, in effect polarizing it. Upon consecutive stampings, the magnitudes of polarization add up, enabling imprinting of multilevel polarization patterns. Because the electric field is high only within the film but low across the Gaussian surface surrounding the film/substrate system, the discharge of surface charges is slow and the polarization patterns are relatively long-lived. These findings are significant since multilevel polarization states have, to date, been achieved only in ferroelectrics or some specialized polymers-the current method extends them to common polymers such as poly(methyl methacrylate), poly(vinyl pyrrolidone), or poly(vinyl acetate).
