In this paper, we propose a novel method for controlling the anisotropic sliding behavior of droplets using multiscale hierarchical structures. First, we employed a silicon wafer mold containing micro-pillars and directional micro-line structures to induce the directional sliding of droplets. Additionally, we fabricated micro-cone patterns and integrated them into the structures to precisely control droplet movement. These two structures were replicated in polymer and subsequently fused into a single multiscale hierarchical mold through a partial curing process. The completed multiscale hierarchical surface was then replicated with PDMS to create anisotropy that governs the direction of droplet movement. We experimentally confirmed that the degree of sliding is influenced by the cone pattern. Our proposed structural design demonstrates that anisotropic wettability control is achievable even on surfaces made from a single material, indicating potential applications in various fields such as microfluidics, sensors, and functional surfaces.
In this paper, we present a simple and robust fabrication method for mushroom-shaped microstructures using diverse polymers with various modulus of elasticity. Through the repeated replica molding process, we fabricated the same PDMS mushroom structure negative mold as the prepared silicon master mold. To evaluate the fabricating stability of the fabricated PDMS negative mold, the mushroom-shaped structures were replicated from the mold using six types of polymer resins with different elastic modulus and we measured superhydrophobic properties on the samples. All the fabricated samples exhibited superhydrophobicity, and we proved the structural stability of the proposed replication method through the measured SEM images, contact angles on the samples, and theoretical analysis based on the structural shape.
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