Research ArticleMATERIALS SCIENCE

Springtail-inspired superomniphobic surface with extreme pressure resistance

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Science Advances  24 Aug 2018:
Vol. 4, no. 8, eaat4978
DOI: 10.1126/sciadv.aat4978
  • Fig. 1 Rational design of a hierarchical system inspired by the springtail cuticle.

    (A) Photograph (courtesy of B. Valentine) of a springtail displaying liquid repellency and resistance to high-pressure raindrops in a flooded habitat (left). SEM images showing the hierarchical system in a springtail cuticle composed of primary and secondary granules (middle and right panels). (B) Schematic of the steps used to fabricate serif-T–shaped nanostructures. Nanoimprinting and the SSL method were used here. The serif-T–shaped nanostructures were made with ~400-nm-diameter dots and ~ 400-nm spacing between the dots, both dimensions similar to those for the primary granules of springtail cuticles. (C) Scheme to fabricate microscale wrinkles via heat-induced shrinkage after nanostructure fabrication.

  • Fig. 2 Morphologies of serif-T–shaped nanostructures on a microscale-wrinkled substrate.

    (A) SEM image of a fabricated hierarchical system with serif-T–shaped nanostructures on a microscale-wrinkled substrate. Inset SEM image shows details of a few serif-T–shaped nanostructures. (B) Cross-sectional view of the hierarchical serif-T system imaged by using a FIB-SEM. The inset in the red box shows a magnified view of a serif-T–shaped structure with a well-made pillar. The inset in the blue box shows only the head of this structure, with the head made hollow to provide a doubly reentrant shape.

  • Fig. 3 Morphological control of nano- and microstructures and corresponding static repellency.

    (A) Hierarchical systems with different kinds of nanostructures. (B) Static contact angles of ethanol on hierarchical systems with control nanostructures. (C) Static contact angles of test liquids (water, ethylene glycol, and ethanol) on the hierarchical serif-T–shaped nanostructures system.

  • Fig. 4 Wetting resistance levels of the hierarchical systems to water drop impact.

    (A) Schematic figures of the hierarchical systems with different nanostructures, and plots of maximum spreading as a function of We for each of these systems. (B) Snapshots of water droplets interacting with two of the systems in (A) using We ~ 110. (C) Schematics of the serif-T system with different microstructure morphologies and plots of maximum spreading as a function of We for each of these systems. (D) Snapshots of water droplets interacting with two of the systems in (C) using We ~ 110. (E) Contact time analysis for various systems (We ~ 220).

  • Fig. 5 Wetting resistance of hierarchical system to impacts by low-surface-tension liquids.

    Comparison of bouncing-off behaviors of ethylene glycol for serif-T nanostructure system on (A) flat and (B) highly wrinkled surfaces. Images of the interactions of ethylene glycol drops with these surfaces are shown. (C) Bouncing behaviors on the serif-T hierarchical system on different levels of microstructures subjected to various applied strains with ethanol impact (We from ~13 to 65). (D) Images of ethanol drops interacting with serif-T hierarchical systems with different microscale morphologies at We ~ 53.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/8/eaat4978/DC1

    Supplementary Text

    Fig. S1. Schematic illustration of gold dot nanopattern fabrication on PS substrate by using conventional nanoimprinting.

    Fig. S2. Schematic illustration of polymer with low surface energy (PHFDMA) coating on structured surface by iCVD.

    Fig. S3. SEM images of nanostructures with different pillar etching condition.

    Fig. S4. Schematic illustration of fabrication for hierarchical system with overhang (reentrant)– and disk-shaped nanostructures.

    Fig. S5. Different morphologies of wrinkled surface with applied areal strain during wrinkling.

    Fig. S6. Advancing and receding contact angles of ethanol on the three different nanostructures.

    Fig. S7. Contact regimes of ethanol droplet on surface with disk-shaped nanostructures and contact angles of various liquids.

    Fig. S8. Fragmentation observation of water droplet with different Weber number (We) on hierarchical system with serif-T–shaped nanostructures.

    Fig. S9. Bouncing-off behaviors after ethylene glycol droplet impacts on highly wrinkled surface with overhang- and serif-T–shaped nanostructures.

    Fig. S10. Contact time analysis of ethylene glycol and water on hierarchical serif-T–shaped nanostructures surface with various We.

    Movie S1. Bouncing behavior of water on the different nanostructures.

    Movie S2. Contact time comparison of water.

    Movie S3. Bouncing test of ethylene glycol on the overhang and the serif-T wrinkles.

    Movie S4. Bouncing test of ethanol on serif-T samples.

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Text
    • Fig. S1. Schematic illustration of gold dot nanopattern fabrication on PS substrate by using conventional nanoimprinting.
    • Fig. S2. Schematic illustration of polymer with low surface energy (PHFDMA) coating on structured surface by iCVD.
    • Fig. S3. SEM images of nanostructures with different pillar etching condition.
    • Fig. S4. Schematic illustration of fabrication for hierarchical system with overhang (reentrant)– and disk-shaped nanostructures.
    • Fig. S5. Different morphologies of wrinkled surface with applied areal strain during wrinkling.
    • Fig. S6. Advancing and receding contact angles of ethanol on the three different nanostructures.
    • Fig. S7. Contact regimes of ethanol droplet on surface with disk-shaped nanostructures and contact angles of various liquids.
    • Fig. S8. Fragmentation observation of water droplet with different Weber number (We) on hierarchical system with serif-T–shaped nanostructures.
    • Fig. S9. Bouncing-off behaviors after ethylene glycol droplet impacts on highly wrinkled surface with overhang- and serif-T–shaped nanostructures.
    • Fig. S10. Contact time analysis of ethylene glycol and water on hierarchical serif-T–shaped nanostructures surface with various We.
    • Legends for movies S1 to S4

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.avi format). Bouncing behavior of water on the different nanostructures.
    • Movie S2 (.avi format). Contact time comparison of water.
    • Movie S3 (.avi format). Bouncing test of ethylene glycol on the overhang and the serif-T wrinkles.
    • Movie S4 (.avi format). Bouncing test of ethanol on serif-T samples.

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