Micro-replication platform for studying the structural effect of seed surfaces on wetting properties

Abstract

Biological surfaces in plants are critical for controlling essential functions such as wettability, adhesion, and light management, which are linked to their adaptation, survival, and reproduction. Biomimetically patterned surfaces replicating the microstructures of plant surfaces have become an emerging tool for understanding plant-environment interactions. In this study, we developed a two-step micro-replication platform to mimic the microstructure of seed surfaces and demonstrated that this initial platform can be used to study seed surface-environment interactions. The two-step process involved the extraction of a simplified seed surface model from real seeds and micro-replication of the simplified seed surface model using nanoimprint lithography. Using Allium seeds collected from Mongolia and Central Asia as the model system, we studied the wettability of biological and synthetic seed surfaces. We could independently control the material properties of a synthetic seed surface while maintaining the microstructures and, thereby, provide clear evidence that Allium seed surfaces were highly wettable owing to the high surface energy in the epidermal material rather than a microstructural effect. We expect that this platform can facilitate study of the independent effect of microstructure on the interaction of seed surfaces with their surroundings and contribute to research on the evolution of plant-environment interactions.

Figure 1

Microscope images of Allium seeds; (a) Image of Allium seed specimens and (b) microscope images of Allium seeds samples 1–25.

Figure 2

The measured contact angle on original and synthetic surfaces of Allium seeds.

Figure 3

Apparent contact angle according to the surface energy of synthetic Allium seed surfaces.

Figure 4

(a) Schematics for particle residues on hydrophilic surfaces. Particle aggregation patterns on (b, c) biological and (d, e) synthetic seed surfaces after drying sprayed droplets of particle-laden solution.

Figure 5

The two-step replication process of Allium seed surfaces. (a) Microscopic image of measured Allium seed surface; (b) first step entails the preparation of Si master mold designed by simplified modeling of seed sur-faces extracted from the measured image and (c) second step involves the replication of the polymeric seed surfaces from the Si master mold using the NIL process.

Figure 6

3D surface profiles of biological and synthetic seed samples; Microscope image and cross-sectional profile of (a) Allium anisotepalum and (b) A. carolinianum seeds; microscope image and cross-sectional profile of the seed surface replicas of (c) A. anisotepalum and (d) A. carolinianum.