Paper PS2-ThM5
Fabrication of Large Superhydrophobic Surfaces with Hierarchical Structures on Polymer Films – Influence of the Roughening and the Fluorination

Thursday, November 10, 2016, 9:20 am, Room 104B

Superhydrophobic (SH) surfaces exhibit many useful characteristics for various industrial applications [1]. Many strategies have been put forward [2] on small surfaces including efficient plasma treatment [3]. It is of great interest to create large and flexible SH surfaces, making polymer films a promising solution. In this work, a two-step method for producing SH large and flexible surfaces from hydrophobic or hydrophilic polymer film materials is described.

Hierarchically structured SH surfaces were fabricated using NIL for submicro scale structuration and plasma treatment for nanoscale structuration. Hydrophobic (FEP) and hydrophilic (PMMA) polymer film materials were used. The roughening of nanoimprinted films by plasma treatment with Ar/CF4 gas flow is reported in a capacitive coupled parallel reactor. Water contact angles (WCA) greater than 160° and contact angle hysteresis (CAH) less than 1° have been measured for a plasma treatment of only 10s. The effect of the input power (600 to 1800 W) has been investigated in terms of roughening and fluorine percentage (%F), see Fig. 1, and Fig. 2 for XPS spectra. This representation enables us to discriminate the influence of the roughness and %F. Indeed, from 800 W plasma treatment, and despite variations of the %F, the wettability remains unchanged due to a sufficient roughness. Fig. 3 shows corresponding SEM images. Additionally, Fig. 4 shows that during plasma treatment, PMMA becomes first hydrophobic as the fluorination increases (from 0 to 39%) and finally superhydrophobic with the increasing roughness.

A modification of the dot dimensions during the plasma treatment is observed as can be seen in Fig. 5. Moreover, fracture defects still remain when fabricating high aspect ratio patterns by NIL [4]. We propose to overpass this limitation by using NIL patterning only as a preliminary step to define the dot diameter. Then the desired height can be achieve by a plasma transfer. Promising results were obtained on rough dots, see Fig. 6.

In the prospect of an industrial application, all process were developed on large areas (50 in² or 320 cm²). Thus, large, flexible and transparent SH films were obtained. Finally, thanks to the combination of NIL and plasma transfer, these films may be used to fabricate high aspect ratio patterns.

This work has been partially supported by the Direction Générale de l’Armement (DGA) and the Renatech network.

[1] Nosonovsky et al. (2009). Current Opinion in Colloid & Interface Sci, 14(4), 270-280

[2] Xue et al. (2016). Sci and Tech of Adv Materials

[3] Durret et al. (2016). Microelectronic Engineering

[4] Schift (2008). Journal of Vacuum Sci & Tech B, 26(2), 458-480