Frequency analysis of micropillar structured surfaces: A characterization and design tool for surface texturing

Various systematically controlled, ordered and randomized micropillar structures were fabricated onto polypropylene by injection molding. Mold inserts were prepared by a micro-working robot. The advantages of this simple surface texturing application include the rigorous control of the pillar positions and the use of a variety of polymers. The textured surfaces were characterized both in horizontal and vertical directions. Power spectral density (PSD) curves combined with filtered root-mean-square (RMS) values provide structure periodicities and roughness differences between various spatial frequencies, respectively. The developed characterization tool is useful in texture mimicking when substantial periodicities and roughness is obtained and imitated in the input data of the micro-working robot. Hence, injection molded micropillar surfaces can possess similar spatial frequency and roughness features to that of mimicked surfaces. The developed characterization method was also connected to the texture design. The height profiles of structures corresponding to the fabricated surfaces were predicted from the experimental input data of the micro-working robot, and the PSD curves were generated to obtain the connection between experimental and predicted structures. The rigorous correspondence between the experimental and predicted structures and the filtered RMS values indicates that the developed design tool enables the theoretical inspection of desired structures. This can also be used in texture mimicking to expedite experimental work.