Contents
Functional, Medical and Electronic Coatings

Self-Healing Elastomer Surface Characterization: Contact Angle on Intrinsic Self-Healing Polymer and Stimuli Responsive Elastomers

Tensile tests show whether a self-healing elastomer recovered its strength. Water contact angle shows whether its surface recovered too: the same wettability, the same chemistry at the top layer, before damage, after damage and after healing.

Who this is for: Polymer chemists and materials R&D teams developing self-healing elastomers, silicones, coatings and soft robotics materials.

Where it fits: Formulation screening, healing studies alongside tensile tests, and tracking surface recovery of silicone after plasma or UV treatment.

What it does not do: It does not measure healing efficiency, tensile strength, toughness or bulk chemistry. Mechanical tests and spectroscopy still decide.

Method
Sessile drop water contact angle on pristine, damaged and healed surfaces; sliding angle for drop mobility
Standard
No ISO or ASTM method for self-healing materials found; contact angle follows ASTM D8597 and D7334 practice
Setup
About 2 minutes
Book a 15 minute demo Request a quote
Elastomers
Why it matters

Why surface recovery deserves its own measurement

97%

healing efficiency in tensile strength after 24 hours at room temperature for an aromatic disulfide polyurethane elastomer, with no catalyst or external trigger.

Rekondo et al., Materials Horizons 1(2):237, 2014

98.4° to 125°

rise in water contact angle on UV responsive bottlebrush silicone elastomers as fluorine spacer content increased, measured on the Dropometer.

Macromolecules, 2025 (customer publication)

10.5 to 33.4 h

half recovery time of water contact angle on silicone elastomer at 25 °C after partial discharge, as low molecular weight chains moved back to the surface.

Kim, Chaudhury and Owen, J. Colloid Interface Sci. 226:231, 2000

Sources: Rekondo A. et al., Materials Horizons, 2014; UV responsive, bottlebrush structured silicone elastomers: synthesis, healing, and application, Macromolecules, 2025; Kim J., Chaudhury M. K., Owen M. J., Journal of Colloid and Interface Science, 2000. Figures come from these sources, not from Droplet Lab measurements.

Quick reference

What this self-healing surface check does and what it does not

A quick reference for elastomer and coating researchers checking fit before reading further.

Evidence Box

Problem this solves

Healed samples that recover strength but not their surface: a scar that wets differently, a coating that loses repellency, a silicone that has not regained hydrophobicity.

Standards

No ISO or ASTM test method for self-healing materials was found, and reviews say methods are not standardized. ASTM D8597 and D7334 cover contact angle itself.

Peer reviewed method

The Dropometer drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, in Review of Scientific Instruments and Colloids and Surfaces A.

Customer case study

Harvard University's Center for Nanoscale Systems shared Dropometer supported seven publications from five labs, including self-healing silicone elastomers.

Customer publication

A Macromolecules (2025) study of UV responsive bottlebrush silicone elastomers measured water contact angle on the Dropometer, five measurements per sample.

Honest limit

Contact angle shows the surface, not the bulk. Healing efficiency still comes from tensile, fracture or hardness tests.

Who this is for

What self-healing question are you trying to answer?

Pick the card closest to your role. Each one points to the part of this page that answers it.

Polymer chemist

You design dynamic bonds: hydrogen bond, disulfide bond, imine, metal ligand or ionic networks. Contact angle on each formulation shows how the chemistry changes the surface, as fluorine and nitrogen spacers did in one published silicone study.

Report drop volume, read time and number of drops with every value.

Materials R&D engineer

You develop self-healing seals, coatings or soft robotics parts. Measuring the surface before damage, after damage and after healing shows whether the healed part will wet, bond and repel like a new one.

Measure beside the healed line as well as on it.

Silicone or coating QC

You plasma or UV treat silicone and need to know when the surface has recovered. Contact angle over hours and days tracks hydrophobic recovery on the same samples.

Record time since treatment and storage temperature.
Fit check

Is this the right check for your self-healing material?

It measures wettability at the surface. It does not measure bulk healing.

Good fit if

You compare the self-healing capabilities and surface chemistry of formulations.
You need to show the surface recovered after healing.
You make self-healing coatings that must stay repellent.
You track hydrophobic recovery of silicone elastomers.
You need a quick screen before tensile tests.

Less relevant if

You need healing efficiency; use tensile or fracture tests.
Your samples are too soft, tacky or curved to hold a drop.
You need chemistry at the scar; use spectroscopy.
The healed line is narrower than a drop.
Summary

How contact angle supports self-healing elastomer research

The answer in under a minute.

Measure water contact angle on each self-healing elastomer when pristine, after damage and after healing, at a fixed read time. A healed value inside the pristine range shows the surface recovered; a shifted value shows the chemistry or texture at the scar changed. Report it beside tensile results as part of self-healing performance, never instead of them.

The Dropometer contact angle kit runs the measurement. A customer study of UV responsive bottlebrush silicone elastomers used it to compare spacer chemistries, and the Harvard University case study shows a shared facility serving elastomer, film and hydrogel labs. The ASTM D8597 page covers portable contact angle measurement, and our contact angle measurement guide explains the method.

Expert Quote

Expert perspective on what the surface shows

Because only the top few ångström decide wetting, an invisible contaminant film, even a monolayer picked up from the air, is enough to change how a liquid behaves on the surface.

Dr. Alidad Amirfazli

Professor, Department of Mechanical Engineering, York University; Co-founder, Scientific Advisor, Droplet Lab

The problem

Why healing is not proven by strength alone

Self-healing polymeric materials, including self-healable elastomers and self-healing rubber, repair damage on their own or under a trigger; that self-healing ability is the point of the material. Extrinsic systems release a healing agent from capsules or channels. Intrinsic self-healing polymers rely on reversible bonds that reform after damage: hydrogen bonds, disulfide bonds, dynamic covalent bonds such as imine or Diels Alder, in which a covalent bond breaks and reforms, metal ligand coordination and ionic interactions. Supramolecular elastomer networks and other autonomous systems heal at ambient conditions, while heat or UV triggered systems such as some self-healing polyurethane need a stimulus, so each follows a different self-healing mechanism and self-healing process. Researchers report self-healing efficiency, or healing performance, as the ratio of healed to original tensile strength in MPa, elongation at break or toughness, alongside modulus and other mechanical properties, and reviews note that the methods are not standardized. Those numbers describe the bulk. They do not show whether the surface came back. A healed elastomer can recover its mechanical strength while the scar has different chemistry, roughness or morphology, so it wets, bonds or repels differently. That matters for self-healing coatings that must stay hydrophobic, seals and soft robotics skins that touch liquids, stretchable sensors where stretchability and adhesion to other layers matter, and silicones whose surface changes after plasma or UV treatment. Silicone adds its own behaviour: after treatment its surface slowly regains hydrophobicity as low molecular weight chains migrate back, over hours to days. Without a surface measurement, a study can report high healing efficiency and still miss a surface that behaves like damaged material.

The healed line wets differently from the rest of the sample.
A self-healing coating loses repellency after repeated damage.
Silicone readings change for days after plasma or UV treatment.
Results vary between batches of the same formulation.
Reviewers ask for evidence beyond tensile healing efficiency.
Troubleshooting

Why the healed surface differs and what to check

Why:

  • Dynamic bonds reform, but different groups can end up at the surface of the healed line.

How to detect:

  • The angle on the scar differs from the pristine range while the angle beside it does not.

Corrective action:

  • Extend healing time or trigger dose, and confirm with spectroscopy at the scar.

Why:

  • Healing can leave a raised, grooved or rougher line, and roughness changes the measured angle.

How to detect:

  • Drops pin or spread unevenly along the line, and spread between drops rises.

Corrective action:

  • Measure beside the line too, and add sliding angle to see drop mobility.

Why:

  • Low molecular weight silicone chains migrate back to a treated or damaged surface over hours to days.

How to detect:

  • The angle on the same sample keeps rising over storage time.

Corrective action:

  • Fix a rest time before measuring, and record time since treatment and storage temperature.

Why:

  • Heat or UV responsive networks need enough time, temperature or dose to reform bonds.

How to detect:

  • Healed values move toward pristine as the trigger dose increases.

Corrective action:

  • Log the trigger conditions and test a dose series alongside tensile tests.

Why:

  • Only the top few ångström decide wetting, so handling or airborne residue changes the reading.

How to detect:

  • Pristine samples drift from batch to batch with no change in formulation.

Corrective action:

Handle samples by the edges and compare with our contact angle reference values. Our page on silicone contamination detection covers residue.

Why:

Drop volume, read time and drop count change the reading. Our guide to reproducible contact angle measurement covers fair comparisons.

How to detect:

  • A reference sample reads differently between sessions.

Corrective action:

  • Fix drop volume, read time and drops per state, and measure a retained reference each session.

Not sure whether your healed surface recovered?

Send pristine and healed samples, and we will compare them on a call.

Book a 15 minute demo
Lab records

What a self-healing surface record contains

Each check produces a record you can file with the formulation and the tensile data for the same samples.

Material

Formulation, healing chemistry, batch, film thickness and cure.

State and history

Pristine, damaged or healed, with the damage method and the healing trigger, time, temperature or UV dose.

Method settings

Drop volume, read time, number of drops, temperature and humidity.

Readings

Contact angle on and beside the healed line, with median and spread.

Linked results

Tensile healing efficiency or hardness recovery for the same samples.

Drop images

Automatic edge and baseline detection gives the same reading from the same image, so a reviewer can recheck any result.

Measurements

What to measure on a self-healing elastomer surface

Baseline

Water contact angle on the pristine surface

Why it matters: It sets the normal range for each formulation and shows how the healing chemistry changes the surface.

How to interpret: Measure several batches; published silicone elastomers in one study ranged from 98.4° to 125° with spacer chemistry. Set your recovery range from your own pristine samples.

When it is not enough: It does not show the bulk network or crosslink density.

Recovery

Angle after damage and after healing

Why it matters: It shows whether the surface returned to the pristine range, a part of healing ability that tensile tests miss.

How to interpret: Compare healed with pristine measured the same way; report the difference with its spread.

When it is not enough: It does not give healing efficiency; that comes from tensile, fracture or hardness tests.

Mobility

Sliding angle

Why it matters: Repellent and slippery surfaces depend on drops moving, not only on a high angle.

How to interpret: Compare drop mobility on pristine and healed areas.

When it is not enough: Tacky surfaces can pin drops and give no clean sliding angle.

Time

Angle over hours and days

Why it matters: Silicone surfaces recover after treatment as low molecular weight chains migrate.

How to interpret: Repeat on the same samples at fixed times and fit the recovery curve.

When it is not enough: It does not separate migration from contamination on its own.

Validation

Validated measurement approach for elastomer surfaces

How the Dropometer itself has been validated, and where customers have used it on elastomers.

Peer reviewed method

The Dropometer drop shape method is published in Review of Scientific Instruments and Colloids and Surfaces A. Contact angle was validated against a KRUSS DSA100E, with a published accuracy of 0.35°.

See the validation papers

Customer evidence on silicone elastomers

A Macromolecules (2025) study of UV responsive bottlebrush silicone elastomers measured water contact angle on the Dropometer with about 5 µL drops and five measurements per sample, and used it to compare fluorine and nitrogen spacers. The study came from a lab using the shared Dropometer at Harvard University's Center for Nanoscale Systems.

Read the citation analysis
QC Protocol

How to check surface recovery on self-healing elastomers

Six steps per sample set. Run them alongside your tensile healing tests.

1

Lock the method

Fix drop volume, read time, drops per state and room conditions; cast flat films of known thickness.

2

Measure pristine samples

Measure several batches to set the normal range. Our wettability glossary entry explains what the angle means.

3

Damage

Cut or scratch by a fixed method, and measure next to the damage.

4

Heal

Apply the trigger, room temperature time, heat or UV dose, and record it.

5

Measure healed samples

After a fixed rest time, measure on and beside the healed line on fresh spots.

We completed our gage R&R study on the unit and it performed very well.

Brandon Barbee

Corporate Quality Engineer, Zeus Industries, Polymer Manufacturing

Download the self-healing elastomer surface SOP

A two page SOP you can adapt for your materials, with the method lock, pristine, damaged and healed steps, recovery criteria, a troubleshooting table and a record sheet.

Contact angle measurement with the Dropometer

Contact angle measurement with the Dropometer

Example output

Example self-healing elastomer surface log

Example data only. Your values and recovery range will differ and must come from your own pristine samples.

How to read this log

Example recovery range: within 5° of pristine. Formulation A recovered strength and surface. Formulation B recovered most of its strength, but the healed line stayed lower in angle, pointing to different chemistry at the scar. Our chemicals guide covers related materials.

Example self-healing elastomer surface log

Formulation Pristine (°) Damaged (°) Healed, on line (°) Healed, beside line (°) Tensile healing efficiency
A 108 96 106 108 Measured separately: high
B 112 95 99 111 Measured separately: high
C 104 90 92 103 Measured separately: low

Example data, not customer data. Cast silicone based films about 100 µm thick; 5 µL water drops read at 2 s; median of 5 drops.

Signal order

The order to check signals on healed samples

Check these in order. Each one rules out a cause before you look at the next.

1

Method and reference

Rules out timing, drop size and handling effects.

2

Pristine range

Shows the normal surface for this formulation.

3

Healed versus pristine

Shows whether the surface recovered.

4

On versus beside the line

Shows whether the scar itself differs.

FAQ

Common questions about self-healing elastomer surfaces

Questions researchers ask about contact angle on self-healing polymers.

An elastomer whose network contains reversible bonds that reform after damage, without an added healing agent. Common chemistries are hydrogen bonds, disulfide bonds, dynamic covalent bonds such as imine or Diels Alder, metal ligand coordination and ionic interactions. Extrinsic systems instead release a healing agent from capsules or channels. Elastomers with self-healing networks can also carry shape memory or other stimuli responsive behaviour found in polymer materials, and their self-healing properties then depend on the trigger.

Most studies divide a healed property by the original one and multiply by 100, usually tensile strength, elongation at break or toughness. One room-temperature self-healing elastomer based on aromatic disulfide chemistry reached 97% after 24 hours at room temperature. Reviews note that these methods are not standardized, so report the property, the damage method and the healing conditions.

Healing efficiency describes the bulk. Contact angle describes the surface: chemistry and texture in the top layer. A healed sample can regain strength while the scar wets differently, which matters for coatings, seals and soft robotics parts that meet liquids. Measure both on the same samples.

We found no ISO or ASTM test method dedicated to self-healing materials, and several reviews say methods are not yet standardized. Contact angle itself is covered by ASTM D7334 for advancing angles and ASTM D8597 for portable goniometers; our ASTM D8597 page explains the second. ASTM D7027 describes a controlled scratch that can standardize the damage step.

After plasma, corona or UV treatment, silicone surfaces become hydrophilic and then slowly regain hydrophobicity. The main mechanism is low molecular weight chains migrating to the surface. One study found half recovery times of 10.5 to 33.4 hours at 25 °C after partial discharge, and much faster recovery at 100 °C.

Some do. Published self-healing superhydrophobic and slippery coatings regain high contact angles or low hysteresis after plasma damage, abrasion or scratches, often after heating or a rest period. Measure static angle and drop mobility, because a repellent surface depends on drops moving as well as beading.

Yes, if the sample holds a drop without deforming much. Cast flat films of known thickness, use a fixed drop volume and read at a fixed early time. Very soft or tacky samples can pin drops, so report spread between drops and add sliding angle only where drops move cleanly.

One that measures water contact angle on films at fixed read times, with small drops and repeat drops per state. The Dropometer does this at the bench, and a Harvard University shared facility used one across elastomer, film and hydrogel projects.

Business impact

What changes when you measure the healed surface

Typical changes in how teams work. Benchmarks are given only where a published source exists.

Before and with surface recovery checks

Metric Before Dropometer With Dropometer Indicative Benchmark
Healing evidence Tensile ratio only Tensile ratio plus surface recovery on the same samples 97% tensile healing at room temperature (Rekondo et al., 2014)
Formulation screening Synthesis then full mechanical tests Contact angle on each formulation first 98.4° to 125° with spacer chemistry (Macromolecules, 2025, Dropometer)
Silicone treatment Measured once after treatment Recovery tracked over hours and days Half recovery 10.5 to 33.4 h at 25 °C (Kim et al., 2000)
Coating repellency Judged by eye Angle and drop mobility after damage and healing No published benchmark; track on your own samples

See the measurement on your own samples

Send pristine and healed samples. We will show the comparison on a call.

Book a 15 minute demo

Estimate saved screening work on self-healing formulations

Enter your own numbers. The result is an estimate, not a Droplet Lab claim.

Self-healing formulation screening estimate

Estimate saved screening work on self-healing formulations.

Each Dropometer unit is US$5,000; the default models one unit.
Your own cost to cast, cut, heal and tensile test one formulation.
Casting, damage, healing and contact angle measurement and analysis.
No published benchmark. Use your own estimate and start low if unsure.

Result

~0
Candidates saved per month
~0
Monthly savings
~0
Payback period
~0
First year net benefit

Monthly savings = materials saved + technician time saved from reduced iterations.

Limits

What contact angle cannot tell you about self-healing

Honest limits, so you know when to reach for another test.

It does not measure healing efficiency.
A healed line narrower than a drop cannot be measured on its own.
Roughness on the scar changes the angle.
Silicone readings drift during hydrophobic recovery.
Soft or tacky samples can pin drops.
No standard method exists for self-healing tests yet.

Contact angle shows whether the surface of a self-healing material recovered its wettability. Healing efficiency and other mechanical properties, bulk chemistry and network structure need their own tests.

Book a 15 minute demo Request a quote
Related

Standards, evidence and related coating workflows

These pages cover the contact angle standard, customer evidence and related surface checks.

Standard

ASTM D8597

Contact angle with portable goniometers.

View use case

Case study

Harvard University

One shared Dropometer, seven publications from five labs.

View use case

Published paper

UV responsive bottlebrush silicone elastomers

Water contact angle measured on the Dropometer.

View use case

Instrument

Dropometer

Contact angle, sliding angle and surface energy.

View use case

Related use case

Functional, medical and electronic coatings

All functional coating use cases in one place.

View use case

Related use case

Silicone contamination detection

Finding invisible silicone residue.

View use case

Related use case

Plated coating wettability

Wettability and corrosion of plated coatings.

View use case

How this page was created

Editorial and technical transparency notes for this page.

Transparency Details 4 checklist items
01

Drafting assistance

Drafted with Claude Opus 5.5 (Anthropic) using web search for sources, then edited by the Droplet Lab team.

02

Technical review

Reviewed and edited for technical accuracy by the Droplet Lab Team.

03

Verification steps

Standard identifiers, units, thresholds and key procedural claims are checked against cited sources before publication.

04

Updates

Reviewed every 12 months or when the underlying method changes.

Report a correction

Spotted an issue in this summary? Send a correction request and our team will review it.

Correction Request

We work hard to keep this page accurate and up to date. If you spot an error (wrong revision/year, missing requirement, incorrect interpretation, or broken link), tell us and we'll review it.

Contact us to report a correction
Sources

References

1.
UV responsive, bottlebrush structured silicone elastomers: synthesis, healing, and application. Macromolecules, 2025. See our citation analysis. https://dropletlab.com/validation/citations/analysis/uv-responsive-bottlebrush-structured-silicone-elastomers-synthesis-healing-and-application/
2.
Rekondo, A. et al. Materials Horizons 1(2):237 to 240, 2014. https://doi.org/10.1039/C3MH00061C
3.
Cordier, P., Tournilhac, F., Soulie Ziakovic, C., Leibler, L. Nature 451:977 to 980, 2008. https://doi.org/10.1038/nature06669
4.
White, S. R. et al. Nature 409:794 to 797, 2001. https://doi.org/10.1038/35057232
5.
Li, C.-H. et al. Nature Chemistry 8(6):619 to 625, 2016. https://doi.org/10.1038/nchem.2492
6.
Utrera Barrios, S., Verdejo, R., Lopez Manchado, M. A., Hernandez Santana, M. Materials Horizons 7:2882 to 2902, 2020. https://doi.org/10.1039/D0MH00535E
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Xu, J. et al. Materials 15(17):5993, 2022. https://doi.org/10.3390/ma15175993
8.
El Choufi, N., Mustapha, S., Tehrani B., A., Grady, B. P. An overview of self healable polymers and recent advances in the field. Macromolecular Rapid Communications 43(17):2200164, 2022. https://doi.org/10.1002/marc.202200164
9.
Paez Amieva, Y., Carpena Montesinos, J., Martin Martinez, J. M. Polymers 15(9):2152, 2023. https://doi.org/10.3390/polym15092152
10.
Lucas, S. S. et al. Journal of Intelligent Material Systems and Structures 27(19):2577 to 2599, 2016. https://doi.org/10.1177/1045389X16641205
11.
Kim, J., Chaudhury, M. K., Owen, M. J. Journal of Colloid and Interface Science 226:231 to 236, 2000. https://doi.org/10.1006/jcis.2000.6817
12.
Kim, J., Chaudhury, M. K., Owen, M. J. IEEE Transactions on Dielectrics and Electrical Insulation 6(5):695 to 702, 1999. https://www.lehigh.edu/~mkc4/our%20papers/Kim_IEEE_1999.pdf
13.
Hillborg, H. et al. Crosslinked polydimethylsiloxane exposed to oxygen plasma studied by neutron reflectometry and other surface specific techniques. Polymer 41(18):6851 to 6863, 2000. https://doi.org/10.1016/S0032-3861(00)00039-2
14.
Shan et al. Soft Matter 16:8473 to 8481, 2020. https://doi.org/10.1039/D0SM01264E
15.
Wong, T.-S. et al. Bioinspired self repairing slippery surfaces with pressure stable omniphobicity. Nature 477:443 to 447, 2011. https://doi.org/10.1038/nature10447
16.
Terryn, S. et al. A review on self healing polymers for soft robotics. Materials Today 47:187 to 205, 2021. https://doi.org/10.1016/j.mattod.2021.01.009
17.
ASTM D8597-24. Standard test method for surface wettability of coatings, substrates, and pigments by contact angle measurement using portable goniometers. See our ASTM D8597 page. https://store.astm.org/d8597-24.html
18.
ASTM D7334-08(2022). Standard practice for surface wettability of coatings, substrates and pigments by advancing contact angle measurement. https://store.astm.org/d7334-08r22.html
19.
ASTM D7027-20. Instrumented scratch testing of polymeric coatings and plastics. https://store.astm.org/d7027-20.html
20.
Chen, X. et al. Contact angle measurement with a smartphone. Review of Scientific Instruments 89(3):035117, 2018. https://pubs.aip.org/aip/rsi/article-abstract/89/3/035117/368179/Contact-angle-measurement-with-a-smartphone
21.
Surface tension measurement with a smartphone using a pendant drop. Colloids and Surfaces A: Physicochemical and Engineering Aspects. https://www.sciencedirect.com/science/article/abs/pii/S0927775717307744
22.
Droplet Lab validation papers
23.
Customer publications that cite the Dropometer
24.
Contact angle measurement guide
25.
Harvard University case study