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  • Flexible-templated imprinti...
    Zhao, Xiaoxiao; Park, Daniel S.; Choi, Junseo; Park, Sungook; Soper, Steven A.; Murphy, Michael C.

    Journal of colloid and interface science, 03/2021, Volume: 585
    Journal Article

    Display omitted Compared to vertical micro-pillars, re-entrant micro-structures exhibited superior omniphobicity for suspending liquids to Cassie-Baxter state. However, the existing re-entrant structures rely on complex multi-step deposition and etching procedures. The conventional, rigid-templated imprinting would instead damage the re-entrant structures. This leads to the question: is it possible to preserve the re-entrant curvatures by a flexible-templated imprinting? We facilely imprinted the re-entrant structures on a plastic substrate using a flexible nylon-mesh template. The effect of imprinting time (15–35 min), temperature (110–120 °C) and pressure (15–50 Bar) was investigated. To further improve the liquid-repellency and abrasion resistance, the silica nanoparticles (30–650 nm) along with epoxy resin binder (10 mg/mL) were pre-coated. A one-step imprinting is sufficient to fabricate the re-entrant structures by utilizing flexible nylon-mesh template, without damaging the imprinted structures after the demolding process. The pre-coated silica nanoparticles and epoxy resin (1) improved liquid repellency by introducing hierarchical surface structures (e.g. contact angle hysteresis of olive oil reduced > 10°), and (2) acted as a protective layer against mechanical abrasion (omniphobicity maintained after 25 cycles, ~1.6 kPa sand paper abrasion). Additionally, the fluorine-free post-treatment was sufficient for the omniphobicity on the obtained plastic structures.