Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces: Study of the Links between Morphology and Wettability.

Quentin Legrand,Stephane Valette,Stephane Benayoun

doi:10.3390/biomimetics6020038

Abstract

This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40 for flat PDMS to less than 10 for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

Highlights

Controlling the wetting properties of surfaces is an important issue for many applications
A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting
As the overall behavior of the leaves is close to replication, it is reasonable to suppose that their wetting configurations are comparable

Summary

Introduction

Controlling the wetting properties of surfaces is an important issue for many applications. According to the fundamental Young’s law of wetting on flat surfaces, many companies developed chemical surface treatments to modify the surface tension of solids and to control their wetting properties. In this sense, industrial very low adhesive surfaces are usually obtained through fluorinated compounds deposition [6,7,8]. The Wenzel [10] and Cassie–Baxter [11] models have highlighted the role of the surface morphology onto the wetting properties of textured surfaces These two fundamental laws have been expanded to take into account more complicated surfaces. One of the most famous examples of low adhesive surface and super-hydrophobicity is the lotus effect, coming from the lotus leaf water repellency

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Discussion

Conclusion