Superhydrophobic Thin Films via Roll-to-Roll iCVD

Journal Pre-proofs
Roll-to roll Initiated Chemical Vapor Deposition of Super Hydrophobic Thin
Films on Large-Scale Flexible Substrates
Hüseyin Şakalak, Kurtuluş Yılmaz, Mehmet Gürsoy, Mustafa Karaman
PII: S0009-2509(19)30956-X
DOI: https://doi.org/10.1016/j.ces.2019.115466
Reference: CES 115466
To appear in: Chemical Engineering Science
Received Date: 27 July 2019
Revised Date: 12 December 2019
Accepted Date: 31 December 2019
Please cite this article as: H. Şakalak, K. Yılmaz, M. Gürsoy, M. Karaman, Roll-to roll Initiated Chemical Vapor
Deposition of Super Hydrophobic Thin Films on Large-Scale Flexible Substrates, Chemical Engineering Science
(2019), doi: https://doi.org/10.1016/j.ces.2019.115466
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Roll-to roll Initiated Chemical Vapor Deposition of Super Hydrophobic Thin Films on
Large-Scale Flexible Substrates
Hüseyin Şakalaka, Kurtuluş Yılmazb, Mehmet Gürsoy1,b,*, Mustafa Karaman1,b,*
a Advanced Materials and Nanotechnology Department, Selcuk University, 42075, Turkey
b Chemical Engineering Department, Konya Technical University, Konya, 42030, Turkey
*Corresponding Authors:
E-mail: [email protected], [email protected]
Phone: +(90) 332 223 2145, +(90) 332 223 2108
Fax: +(90) 332 241 0635
Postal address: Department of Chemical Engineering, Konya Technical University, Campus,
Konya 42030, Turkey
1 These corresponding authors have made equal contributions.

Abstract
In this study, a large-scale roll-to-roll initiated chemical vapor deposition (iCVD) system was
developed to allow for coating superhydrophobic thin films on flexible substrates.
Poly(hexafluorobutyl acrylate), which possesses a short fluorinated side-chain, was chosen as
the hydrophobic finish material, while a commercial porous bamboo fabric was used as the
flexible substrate. After iCVD coating, bamboo surface, which is superhydrophilic by its
nature, transformed into a superhydrophobic with a water contact angle of 156° without
changing its porous and flexible structure. Similar hydrophobic properties were observed
against various daily liquids. Complete coverage of as-deposited films on both sides of
bamboo surfaces was observed at very high roll speeds up to 225 mm/min, which allow
coatings on 20 m2 flexible substrates in a single run. Large scale contact angle and chemical
uniformity of coatings on fabric surfaces were evaluated using contact angle and XPS
analyses.
Keywords: iCVD, Superhydrophobic, Roll-to-roll, Polymer, Thin film
Graphical abstract

Highlights
A roll-to-roll iCVD system was designed.
Superhydrophobic coatings were deposited on bamboo surfaces.
High roll speeds up to 225 mm/min was achieved.
As-deposited polymers were conformal and uniform.

1. Introduction
In last decades, the emergence of flexible electronics for variety of applications, such as
flexible displays, flexible circuits, flexible sensors and flexible solar cells, has led to increased
need for large-scale production processes (Dubal et al., 2018; Lee and Yoo, 2012; Yang and
Gao, 2019). Other than the electronics field, flexible substrates are used in a wide variety of
applications such as membranes, food packaging, artificial skins, microfluidics, etc (Lei and
Wu, 2019; Yang et al., 2019). In general, roll-to-roll systems are preferred to the conventional
batch systems to coat flexible substrates in a continuous manner for the mass production of
many important products (Gao et al., 2016; Guerrero et al., 2011; Maydannik et al., 2011).
When compared with the batch systems, roll-to-roll systems offer significant cost reduction
considering the high yield and large utilized surface area (Kovacik et al., 2015).
The interest in functional polymeric coatings has recently experienced rapid growth
within both the research and industrial community because of their flexible properties (Chen
et al., 2013; Gürsoy et al., 2017b). Functional coatings add desired properties on the surface
of substrates without changing the bulk. Polymer coating processes can be divided into two
main categories, namely wet and dry techniques. In the former ones, the coating material and
a suitable binder are dissolved in a solution that is directly coated on the substrate. The
evaporation of solvent from the wet film results in a dry and stringent coating on substrate
surface. Drop casting, spin coating, dip coating, sol-gel, and spray coating are among the most
utilized coatings for various applications (Danglad-Flores et al., 2018; Schlaich et al., 2018;
Wedershoven et al., 2018). In dry techniques, as its name implies, the usage of solvents is
ruled out, and coating material is directly deposited on the substrate surface through
condensation of vapor-phase precursors (Gürsoy et al., 2019). Physical vapor deposition
(PVD) and chemical vapor deposition (CVD) techniques are widely used dry techniques for
coating thin, conformal, and uniform films on many different types of substrates. Such vapor