ISO/TS 10689:2023
(Main)Nanotechnologies — Superhydrophobic surfaces and coatings: Characteristics and performance assessment
Nanotechnologies — Superhydrophobic surfaces and coatings: Characteristics and performance assessment
This document specifies requirements and recommendations for performance assessment methods for superhydrophobic surfaces and coatings subjected to mechanical stress, solar radiation and weathering, liquids, and thermal cycling, where applicable, based on the agreement between interested parties. The performance assessment is carried out based on comparative measurements of the advancing and receding angles and the calculation of the contact angle hysteresis before and after the above-mentioned working/environmental conditions. This document does not address safety and environmental related issues of such coatings. This document is applicable to any superhydrophobic surfaces and coatings (i.e. nanostructured) on which the measurement of the advancing and receding angles is possible.
Nanotechnologies — Surfaces et revêtements superhydrophobiques : Caractéristiques et évaluation de la performance
General Information
Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 10689
First edition
2023-08
Nanotechnologies —
Superhydrophobic surfaces and
coatings: Characteristics and
performance assessment
Nanotechnologies — Surfaces et revêtements superhydrophobiques :
Caractéristiques et évaluation de la performance
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Characteristics and measurement methods . 5
4.1 General . 5
4.2 Test piece . 5
4.3 Pre-treatment of the test piece . 6
4.4 Contact angle measurement — Dynamic method . 6
4.4.1 Advancing angle . 6
4.4.2 Receding angle . 6
4.4.3 Contact angle hysteresis . 6
4.5 Wettability regions . 6
5 Procedure .8
5.1 General . 8
5.2 Mechanical stress methods . 8
5.2.1 Water impacting test . 8
5.2.2 Wear resistance tests . 10
5.3 Determination of the resistance to solar radiation and weathering .12
5.3.1 General .12
5.3.2 Specimen preparation and conditioning .12
5.3.3 Procedure .13
5.3.4 Test report .13
5.4 Determination of resistance to liquids . 13
5.4.1 General .13
5.4.2 Preparation . 14
5.4.3 Procedure . 14
5.4.4 Test report . 14
5.5 Thermal cycling test . 14
5.5.1 General . 14
5.5.2 Procedure . 14
5.5.3 Test report .15
Annex A (informative) Superhydrophobic surfaces and coatings .16
Annex B (informative) Recommended standard test methods .18
Bibliography .19
iii
Foreword
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iv
Introduction
Surfaces or coatings which are extremely difficult to wet with water can be considered as
superhydrophobic. Based on the scientific literature, superhydrophobic surfaces and coatings show
contact angles of above 150° as well as contact angle hysteresis less than 10°. Superhydrophobicity
phenomena is seen in some natural species, e.g. lotus leaves. Another related term is “lotus effect”
which arises for droplets in the Cassie-Baxter wetting state.
Various methods have been utilized for the production of superhydrophobic surfaces and coatings,
e.g. chemical vapour deposition, spin coating, sputtering, plasma deposition, chemical etching, sol-gel,
photolithography, anodizing and plasma electrolyte oxidation. The superhydrophobic surfaces and
coatings have numerous applications in different industries due to their properties, which can include
self-cleaning, anti-corrosion, anti-icing, anti-fog and antibacterial effects. Such coatings and surfaces are
gradually entering automotive, building and construction, healthcare, optical and electrical industries.
[1]
The market for superhydrophobic surfaces and coatings for 2020 was about $1,8 billion .
A common characteristic of superhydrophobic surfaces and coatings is their proper two-level
topography (i.e. micro- and nano-sized asperities) combined with low surface energy. This multiscale
(hierarchical) roughness would result in large water contact angle, low contact angle hysteresis, and
high wetting stability against the Cassie–Baxter to Wenzel transition. In other words, a large contact
angle is already achievable with a microscale surface roughness but for having a large contact angle
[3]
combined with small contact angle hysteresis, nanoscale roughness is needed . In other words, water
cannot penetrate into nano-scale surface asperities which results in small contact angle hysteresis. In
the absence of nano roughness, penetration of water into the micro-scale surface asperities results in
high contact angle hysteresis (see Annex A). Such surfaces (surfaces with contact angles above 150°
[3]
and contact angle hysteresis more than 10°) are called “pseudo-superhydrophobic” surfaces ; another
related term for pseudo-superhydrophobic is “sticky superhydrophobic”, that arises due to the rose
petal effect for droplets being in the Wenzel state.
Water droplets easily bead up and roll-off on superhydrophobic surfaces and coatings and this easy
roll-off is the root cause of all the interesting properties of superhydrophobic surfaces and coatings.
Advancing and receding angles are the parameters used to quantify the droplet mobility on surfaces. As
such, measuring the advancing and receding angles identifies if a coating/surface has superhydrophobic
properties. Also, measuring the advancing and receding angles before and after exposing the
surface to different working/environmental conditions can be used to assess the performance of
superhydrophobic surfaces and coatings.
The superhydrophobic surfaces and coatings are normally subjected to different working/
environmental conditions, for example, mechanical stress, ultra-violet (UV), visible and infrared (IR)
exposure, exposure to different liquids and thermal cycling. These conditions may lead to possible
alteration of the performance of superhydrophobic surfaces and coatings. Unfortunately, despite the
huge market, there is currently no standard to assess the durability of superhydrophobic surfaces
and coatings. This document aims to specify performance assessment methods of superhydrophobic
surfaces and coatings under different working/environmental conditions, where applicable, based on
the agreement between interested parties. The assessment criteria are comparison of advancing angle,
receding angle and contact angle hysteresis of the samples before and after being subjected to the above-
mentioned working/environmental conditions. Further, this document facilitates the communication
between the interested parties. Also, this document supports UN sustainable development goals (SDGs)
8 and 12 which are “decent work and economic growth” and “responsible consumption and production”.
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