Nanotextures play increasingly important roles in nanotechnology. Recent studies revealed that their functionalities can be further enhanced by spatially modulating the height of their nanoscale pixels. Realizing the concept, however, is very challenging as it requires "grayscale" printing of the nanopixels in which their height is controlled within a few nanometers as a micrometric function of position. This work demonstrates such a high vertical and lateral resolution grayscale printing of polymeric nanopixels. We realize the height modulation by exploiting the discovery that the capillary rise of certain photopolymers can be optically controlled to stop at a predetermined height with sub-10-nm accuracy. Microscale spatial patterning of the control light directly extends the height modulation into a two-dimensionally patterned, grayscale nanopixel printing. Its utility is verified through readily reconfigurable, maskless printing of grayscale nanopixel arrays in dielectric and metallo-dielectric forms. This work also reveals the highly nonlinear and unstable nature of the polymeric nanocapillary effect, expanding its understanding and application scope.
Keywords: digital micromirror device; gap plasmonics; maskless photolithography; nanocapillarity; nanofabrication; optofluidics.