Multi-height structures in injection molded polymer

Three consecutive etching steps resulting in multi-height structures from overlapping etches.Display Omitted We present the fabrication of injection molded multi-height surface structures.We use a random mask, diffusion limited growth and electroforming a polymer foil.We find that the receding contact angle governing contact angle hysteresis.We find that introduction of pinning sites dominates the wetting behavior. We present the fabrication process for injection molded multi-height surface structures for studies of wetting behavior. We adapt the design of super hydrophobic structures to the fabrication constrictions imposed by industrial injection molding. This is important since many super hydrophobic surfaces are challenging to realize by injection molding due to overhanging structures and very high aspect ratios. In the fabrication process, we introduce several unconventional steps for producing the desired shapes, using a completely random mask pattern, exploiting the diffusion limited growth rates of different geometries, and electroforming a nickel mold from a polymer foil. The injection-molded samples are characterized by contact angle hysteresis obtained by the tilting method. We find that the receding contact angle depends on the surface coverage of the random surface structure, while the advancing contact angle is practically independent of the structure. Moreover, we argue that the increase in contact angle hysteresis correlates with the concentration of pinning sites among the random surface structures.