A fast, precise and low-cost replication technique for nano- and high-aspect-ratio structures of biological and artificial surfaces

Abstract

Biological surfaces are multifunctional interfaces between the organisms and their environment. Properties such as the wettability and adhesion of particles are linked to the micro- and nanostructures of their surfaces. In this study, we used plant and artificial surfaces covered with wax crystals to develop a low-cost replication technique with high resolution. The technique is applicable for fragile surface structures, as demonstrated for three-dimensional wax crystals, and is fast to prevent shrinking of the biological material by water loss during the molding process. Thermal evaporation of octacosan-1-ol has been used to create microstructured surfaces with small platelets as templates for molding. Epoxy resin as filling material provided the smallest deviations from the original surface structures and can be used for replication of nanostructures as small as 4.5 nm. Contact angle measurements of leaves and their replicas show that this technique can be used to develop biomimetic surfaces with similar wettability as in the plant surfaces.

Attachment to challenging substrates – fouling, roughness and limits of adhesion in the northern clingfish (Gobiesox maeandricus)

“…In contrast to natural substrates, they provide not only a homogeneous surface roughness, but also identical material properties because all surfaces were created with the same material. We used a mold made from a smooth glass surface and three different types of sandpaper (P320, P180 and P60; Buehler ® Carbimet, Lake Bluff, IL, USA, matching grain sizes of 35, 78 and 269 μm) using dental wax (President Light Body, Coltene Whaledent, Lagenau, Germany), and then cast surfaces in epoxy resin (Low Viscosity Spurr Kit, SPI Supplies ® , West Chester, PA, USA) in accordance with Koch (Koch et al, 2008). To let fouling organisms grow on the substrates, we exposed 10 surfaces of each roughness type (primary surface roughness) for a time span of 6 weeks (June-July) in the Salish Sea at Friday Harbor Laboratories, WA, USA.…”

Bioinspired hook surfaces based upon a ubiquitous weed (Galium aparine) for dry adhesion

“…Negative moulds from each of these surfaces were prepared by application of a polyvinylsiloxane base and cure mixture (President Plus Jet Light Body, Coltene/Whaledent AG) to the substrate, 29,30 and then immediately pressing down on top using a glass slide for the duration of the 10 min cure period. Once the negative mould had hardened, it was carefully peeled away from the natural substrate surface, rinsed with water, and left to dry.…”

The insect-trapping rim of Nepenthes pitchers

“…To reach a quantitative understanding of the function of the peristome, more detailed data on insect adhesion and on the surface chemistry of the peristome are needed. The fabrication of high-resolution surface replicas 43 might make it possible to separate experimentally between the effects of surface chemistry and topography. Moreover, modern micro/nanofabrication techniques provide a tool to create artificial surfaces that mimic the topography of the peristome.…”