Water-Based Peeling of Thin Hydrophobic Films

Sepideh Khodaparast, François Boulogne, Christophe Poulard, and Howard A. Stone

Phys. Rev. Lett. 119, 154502 – Published 13 October 2017; Erratum Phys. Rev. Lett. 121, 269901 (2018)

Abstract

Inks of permanent markers and waterproof cosmetics create elastic thin films upon application on a surface. Such adhesive materials are deliberately designed to exhibit water-repellent behavior. Therefore, patterns made up of these inks become resistant to moisture and cannot be cleaned by water after drying. However, we show that sufficiently slow dipping of such elastic films, which are adhered to a substrate, into a bath of pure water allows for complete removal of the hydrophobic coatings. Upon dipping, the air-water interface in the bath forms a contact line on the substrate, which exerts a capillary-induced peeling force at the edge of the hydrophobic thin film. We highlight that this capillary peeling process is more effective at lower velocities of the air-liquid interface and lower viscosities. Capillary peeling not only removes such thin films from the substrate but also transfers them flawlessly onto the air-water interface.

Received 3 July 2017

DOI:https://doi.org/10.1103/PhysRevLett.119.154502

Physics Subject Headings (PhySH)

Applications of soft matter Flexible electronics

Annealing Film deposition Optical techniques Sample preparation

Polymers & Soft MatterGeneral PhysicsFluid Dynamics

Erratum

Erratum: Water-based Peeling of Thin Hydrophobic Films [Phys. Rev. Lett. 119, 154502 (2017)]

Sepideh Khodaparast, François Boulogne, Christophe Poulard, and Howard A. Stone

Phys. Rev. Lett. 121, 269901 (2018)

Authors & Affiliations

Sepideh Khodaparast¹, François Boulogne^1,2, Christophe Poulard², and Howard A. Stone^1,*

¹Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
²Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris–Saclay, Orsay 91400, France

^*hastone@Princeton.edu

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Issue

Vol. 119, Iss. 15 — 13 October 2017

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Images

Figure 1
Myth of the Sharpie. (a) The letters PU, written on a glass substrate with a red permanent Sharpie marker, are peeled off and transferred onto the air-water interface as the glass substrate is slowly dipped into a water bath. Patterns printed using Sharpie markers on glass are otherwise resistant to rinsing with water after drying. See the movies in the SM [19]. (b) A similar phenomenon is observed for a dried droplet of terpene phenolic resin (SYLVARES TP 2040). For visualization, a small amount of rhodamine-B dye is added to the terpene phenolic resin. The advancing air-water interface moves at the speed $U = 1 μ m / s$ .
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Figure 2
Understanding capillary-driven peeling. (a) Schematic of the configuration used in the capillary peeling experiments. (b) Experimental visualizations of the main steps of the capillary peeling process. The liquid phase is labeled with a red fluorescent dye and the thin PS film ( $b = 200 nm$ ) is covered with polystyrene microparticles to reflect the green light of the laser used in the experiments. The air-water interface moves with speed $U = 1 μ m / s$ on the substrate. The contact angle $θ (t)$ changes from the advancing value $θ_{a}$ on the clean substrate to the $θ_{p}$ as the crack propagates in a steady-state manner. (c) On the hydrophilic glass substrate, water exhibits a split-injection flow pattern with a stagnation point at the contact point. (d) The time evolution of the experimental measurements of the height $H$ and the angle $θ$ of the liquid wedge confirms the distinct regimes present in a successful capillary peeling process.
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Figure 3
Role of viscous effects. (a) Capillary peeling becomes less efficient at higher speeds $U > 1 mm / s$ , especially for very thin films $b < 100 nm$ . The success rate is calculated for capillary peeling performed on 20 samples. (b) Velocity dependence of the adhesion energy $G$ and the viscous effects. The blue domain corresponds to an energetically favorable peeling. (c) Capillary peeling becomes less efficient at higher viscosities $η \approx 10^{- 2} Pa s$ for $b = 850 nm$ . (d) The data from (c) collapse when plotted as a function of $η U$ . Capillary peeling tends to fail for $η U > 10^{- 2} N / m$ .
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Figure 4
Applications of capillary peeling. (a) Large-area thin films ( $b = 200 nm$ ) can be (1) detached from the substrate, and (2) flawlessly transferred to the air-water interface. (3) Such thin films are otherwise difficult to handle or transferred to another substrate. (b) Complex patterns can be (1) detached from the original substrate, (2) moved onto the air-water interface, and, finally, (3-1),(3-2) transferred onto unconventional substrates. Here, marks made by Sharpie pens are transferred to (3-1) the curved surface of a small glass bottle and (3-2) the delicate surface of a color contact lens. (c) Waterproof thin films can be removed from unconventional curved substrates. Here, the mark made by a Sharpie pen is removed from the outer wall of a laboratory tube.
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