Straightforward and precise approach to replicate complex hierarchical structures from plant surfaces onto soft matter polymer

Abstract

The surfaces of plant leaves are rarely smooth and often possess a species-specific micro- and/or nano-structuring. These structures usually influence the surface functionality of the leaves such as wettability, optical properties, friction and adhesion in insect–plant interactions. This work presents a simple, convenient, inexpensive and precise two-step micro-replication technique to transfer surface microstructures of plant leaves onto highly transparent soft polymer material. Leaves of three different plants with variable size (0.5–100 µm), shape and complexity (hierarchical levels) of their surface microstructures were selected as model bio-templates. A thermoset epoxy resin was used at ambient conditions to produce negative moulds directly from fresh plant leaves. An alkaline chemical treatment was established to remove the entirety of the leaf material from the cured negative epoxy mould when necessary, i.e. for highly complex hierarchical structures. Obtained moulds were filled up afterwards with low viscosity silicone elastomer (PDMS) to obtain positive surface replicas. Comparative scanning electron microscopy investigations (original plant leaves and replicated polymeric surfaces) reveal the high precision and versatility of this replication technique. This technique has promising future application for the development of bioinspired functional surfaces. Additionally, the fabricated polymer replicas provide a model to systematically investigate the structural key points of surface functionalities.

In Situ Investigation of Adhesion Mechanisms on Complex Microstructured Biological Surfaces

“…Figure 1d) with a diameter of about 50–100 µm and a height of about 50 µm. [ 80 ] Lychee ( Litchi chinensis ; abaxial, i.e., lower leaf surface) has a complex hierarchical surface structuring (cf. Figure 1g) consisting of “rose‐flower‐shaped” units inducing undercuts and overhanging substructures.…”

“…2018, which uses epoxy resin for generating negative moulds and producing the final replica on polydimethylsiloxane (PDMS) substrates. [ 80 ] The force range that corresponds to plant–insect interactions falls in the few mN range, and therefore calls for a precise experimental setup. [ 45,93,94 ] Such a low force range and high sensitivity can be accomplished with a nanoindenter like apparatus.…”

“…[ 52–54,56 ] Nevertheless, several papers have been published offering different methodological approaches to replicate the surface structures directly from original plant leaves onto the various polymeric substrates. [ 80–85 ]…”

Spatiotemporal development of cuticular ridges on leaf surfaces ofHevea brasiliensisalters insect attachment

“…For leaf surface replication, an Epoxy-PDMS replication method as described in Kumar et al, 2018 [34] was used, except that entire leaf laminas (min. leaf lamina area = 1168 mm 2 , max.…”

“…For comparisons, five clean glass slides were also replicated and, henceforth, we term the replicas of glass as 'flat PDMS'. The efficiency of replication of young and adult H. brasiliensis leaves was as quantified in Kumar et al, 2018 [34] to which we also refer the interested reader for further details concerning the process.…”