ISO/TS 10689:2023

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

• Status: Published
• Publication Date: 07-Aug-2023
• ICS: 07.120 - Nanotechnologies
• Technical Committee: ISO/TC 229 - Nanotechnologies
• Drafting Committee: ISO/TC 229 - Nanotechnologies
• Current Stage: 6060 - International Standard published
• Start Date: 08-Aug-2023
• Due Date: 08-Jul-2025
• Completion Date: 08-Aug-2023

Overview

ISO/TS 10689:2023 - Nanotechnologies - Superhydrophobic surfaces and coatings: Characteristics and performance assessment - specifies methods to assess the performance of superhydrophobic surfaces and coatings (nanostructured) when exposed to mechanical stress, solar radiation and weathering, liquids, and thermal cycling. The standard defines a comparative, measurement-based approach: advancing and receding contact angles are measured and contact angle hysteresis is calculated before and after exposure to agreed test conditions. ISO/TS 10689:2023 applies where advancing/receding angle measurements are possible and does not cover safety or environmental aspects.

Key topics and requirements

• Performance assessment principle: comparative measurements of advancing angle, receding angle and calculation of contact angle hysteresis pre‑ and post‑exposure.
• Definition of superhydrophobicity: typically contact angle > 150° and contact angle hysteresis < 10° (introductory guidance).
• Measurement method: dynamic contact angle techniques (advancing/receding) as the primary quantitative metric for droplet mobility and wetting state.
• Environmental and mechanical tests:
  • Mechanical stress (e.g., water impact, wear resistance)
  • Resistance to solar radiation and weathering
  • Resistance to liquids (immersion/chemical exposure)
  • Thermal cycling
• Specimen preparation and conditioning: procedures and pre‑treatment to ensure valid comparative results (as agreed between parties).
• Reporting and acceptance: test reports should document pre/post contact angles, hysteresis, test conditions and agreed pass/fail criteria.
• Applicability: any nanostructured superhydrophobic surface/coating where advancing/receding angle measurement is feasible.
• Scope limits: does not address safety, environmental impacts, or detailed production processes.

Practical applications and who uses it

ISO/TS 10689:2023 supports objective durability and performance claims for superhydrophobic products. Typical users include:

• Coating manufacturers validating product durability (self‑cleaning, anti‑icing, anti‑fog, anti‑corrosion)
• Quality assurance and test laboratories performing comparative contact‑angle testing
• OEMs and specifiers in automotive, building & construction, healthcare, optical and electrical industries requiring performance data
• R&D and materials scientists developing hierarchical (micro/nano) surface structures
• Procurement and certification bodies seeking standardized test evidence for product specifications

Related standards

ISO/TS 10689 references relevant test and measurement documents, including:

• ISO 19403‑6 (dynamic contact angle measurement)
• ISO 16474‑2 (xenon‑arc weathering methods)
• ISO 2812‑1 (resistance to liquids)
• ISO 7784‑3 (abrasion/wear resistance)
• ISO 11997‑3 (cyclic corrosion testing)
• ISO/TR 21555 (overview of hardness/wear test methods)

ISO/TS 10689:2023 helps stakeholders compare and communicate superhydrophobic performance consistently by focusing on measurable wetting metrics and agreed test conditions.

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
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
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
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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”.
v
TECHNICAL SPECIFICATION ISO/TS 10689:2023(E)
Nanotechnologies — Superhydrophobic surfaces and
coatings: Characteristics and performance assessment
1 Scope
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.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2812-1, Paints and varnishes — Determination of resistance to liquids — Part 1: Immersion in liquids
other than water
ISO 7784-3, Paints and varnishes — Determination of resistance to abrasion — Part 3: Method with
abrasive-paper covered wheel and linearly reciprocating test panel
ISO 11997-3, Paints and varnishes — Determination of resistance to cyclic corrosion conditions — Part 3:
Testing of coating systems on materials and components in automotive construction
ISO 16474-2, Paints and varnishes — Methods of exposure to laboratory light sources — Part 2: Xenon-arc
lamps
ISO 19403-6:2017, Paints and varnishes — Wettability — Part 6: Measurement of dynamic contact angle
ISO/TR 21555:2019, Paints and varnishes — Overview of test methods on hardness and wear resistance of
coatings
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
abrasion
wear which is caused by removal of coating materials on a surface
[SOURCE: ISO/TR 21555:2019, 3.6]
3.2
advancing angle
θ
a
contact angle (3.3), which is measured during advancing of the three-phase point
Note 1 to entry: Generally, the advancing angle is used for the determination of the interface energy, in which
case, the measurement should be carried out close to the thermodynamic equilibrium. This is approximately
reached if there is no influence of, for example, the dosing speed on the contact angle.
Note 2 to entry: See Figure 1.
Key
advancing angle
θ
a
Figure 1 — Illustration of an advancing angle by needle application of a drop
[SOURCE: ISO 19403-6:2017, 3.2, modified — Note 2 to entry has been added.]
3.3
contact angle
θ
angle to the base line within the drop, formed by means of a tangent on the drop contour through one of
the three-phase points
Note 1 to entry: see Figure 2.
Key
1 three-phase point
2 liquid phase
3 solid phase
4 gas phase
5 base line
surface tension of the liquid surface
σ
l
surface free energy of the solid surface
σ
s
interfacial energy between solid surface and liquid surface
σ
sl
contact angle
θ
Figure 2 — Illustration of a contact angle in wetting equilibrium
o
Note 2 to entry: The contact angle is preferably indicated in degrees (°). 1 =π /180 . If the system is in
thermodynamic equilibrium, this contact angle is also referred to as thermodynamic equilibrium contact angle.
[SOURCE: ISO 19403-1:2022, 3.1.9, modified — the title of Figure 2 has been slightly modified.]
3.4
contact angle hysteresis
θ
ar
difference between advancing angle (3.2) and receding angle
[SOURCE: ISO 19403-6:2017, 3.4]
3.5
chemical homogeneity
chemically homogeneous composition of a surface to be examined
Note 1 to entry: The definition regards a purely qualitative assessment of the surface. Regarding the measurement
of the contact angle (3.3), a surface is considered chemically and topologically sufficiently homogeneous if no
significant differences of the contact angles can be determined when measuring on several areas on the surface.
The significance limits can be specified by the user in accordance with standard laboratory methods.
[SOURCE: ISO 19403-1:2022, 3.1.1, modified — "locations" has been replaced with "areas" in Note 2 to
entry.]
3.6
double stroke
ds
complete reciprocal movement made by the abrasive wheel
[SOURCE: ISO 7784-3:2022, 3.2]
3.7
dynamic contact angle
contact angle (3.3), which is measured during advancing or receding of the three-phase point
Note 1 to entry: The advancing or receding of the three-phase point can be achieved by changing the volume of
the liquid drop to be measured, by relative movement (immersing and pulling out) of a solid body to an interface,
or by moving the drop over the interface (e.g. rolling off).
[SOURCE: ISO 19403-6:2017, 3.1]
3.8
receding contact angle
θ
r
contact angle (3.3), which is measured during receding of the three-phase point
Note 1 to entry: See Figure 3.
Key
receding angle
θ
r
Figure 3 — Illustration of receding angle by needle extraction of a drop
[SOURCE: ISO 19403-6:2017, 3.3, modified — Note 1 to entry has been added.]
3.9
static contact angle
angle between a plane solid surface and the tangent drawn in the vertical plane at the interface between
the plane solid surface and the surface of a droplet of liquid resting on the surface
[SOURCE: ISO 15989:2004, 3.4, modified — the symbol "θ" has been deleted.]
3.10
superhydrophobic coating
coated surface for which the contact angle (3.3) with a water droplet exceeds 150° and contact angle
hysteresis (3.4) is less than 10°
3.11
superhydrophobic surface
surface made from hydrophobic material having nano-scale textures for which the contact angle (3.3)
with a water droplet exceeds 150° and the contact angle hysteresis (3.4) is less than 10°
3.12
topological homogeneity
uniformity of the macroscopic surface, including evenness and smoothness
Note 1 to entry: The definition regards a purely qualitative assessment of the surface. Regarding the measurement
of the contact angle (3.3), a surface is considered chemically and topologically sufficiently homogeneous if no
significant differences of the contact angles can be determined when measuring on several areas on the surface.
The significance limits can be specified by the user in accordance with standard laboratory methods.
[SOURCE: ISO 19403-1:2017, 3.1.2]
3.13
wear
irreversible change of a coating which is caused by the mechanical impact of moved objects
[SOURCE: ISO/TR 21555: 2019, 3.2]
3.14
wettability
degree of wetting
o
Note 1 to entry: Contact angle (3.3) θ = 0 indicates fully wetted and θ =180 indicates not wetted.
[SOURCE: ISO 19403-1:2017, 3.3.2, modified — Note 1 to entry has been added.]
4 Characteristics and measurement methods
4.1 General
The contact angle of water on superhydrophobic surfaces and coatings is larger than 150° and contact
angle hysteresis is less than 10°. Measuring the static contact angle on a superhydrophobic surface/
coating according to ISO 19403-2:2017, 7.2.2 is not possible (or at least it is challenging) as the drop
adheres to the needle and detaches from the surface during the procedure. As such, only dynamic
method (advancing and receding angles) shall be used. In other words, the following characteristics
shall be measured/calculated and reported after each test: advancing angle, receding angle and contact
angle hysteresis. The superhydrophobic surfaces and coatings to be tested for this document shall be
rigid, planar, macroscopically homogeneous and macroscopically smooth, on which measuring the
advancing and receding angles (dynamic contact angles) in accordance with ISO 19403-6 is possible.
A commercially available contact-angle meter, including a light source, optical system, specimen stage,
automatic liquid delivery system, and image processing algorithm is used according to ISO 19403-6.
4.2 Test piece
Cut out flat pieces of the substrate coated by superhydrophobic coating or substrate with
superhydrophobic surface. The cut pieces shall be proper representatives of the whole material used in
the real-world application. Caution shall be made not to contaminate the test piece with contaminants.
The shape and size of the test piece should allow the measurement of the advancing/receding angle
at minimum five different points, also allow performing the required tests mentioned in Clause 5 and
agreed by interested parties.
4.3 Pre-treatment of the test piece
Measurements and determination of contact angle is extremely surface sensitive, especially to any
contamination. The risk of measuring useless results is therefore immense. Store the test pieces when
they will not be used immediately. Storage depends on the superhydrophobic material and substrate;
storage specifications shall be agreed upon by the interested parties.
4.4 Contact angle measurement — Dynamic method
4.4.1 Advancing angle
The advancing angle shall be measured in accordance with ISO 19403-6. In this method, by adding
the test liquids (i.e. water) to a drop on a surface, advancing angles are measured. The measurement
should be carried out close to the equilibrium. The standard deviation for the advancing angle should
not be more than 5°. In case the standard deviation is more than 5° for the dynamic method, the surface
chemical and topological homogeneities shall be checked. In order to improve the reliability, the mean
value can be calcul
...