tensiometer - ATA Scientific

Surface tension measurement in batteries refers to analysing how liquids such as electrode slurries and electrolytes interact with solid surfaces like electrodes, separators, and casings. It’s a critical factor in manufacturing and R&D because it governs wetting, coating uniformity, adhesion, and material compatibility.

In this guide, we will share the essential methods for measuring surface tension and delve into its crucial role in advancing battery manufacturing and performance.

This guide will help you:

Understand why surface tension is important for battery manufacturing and research
Learn the main methods for measuring surface tension in liquids and solids
Match each method to the right KRÜSS instrument for your application
See how surface tension measurement fits into battery R&D and quality control workflows

By the end, you’ll know which technique to use, when to use it, and how it supports consistent, reliable battery production.

What is Surface Tension?

Surface tension, interfacial tension, and surface free energy (SFE) are closely related properties in surface and colloid science. Surface tension is the cohesive energy at a liquid’s interface, while interfacial tension describes the same phenomenon between two immiscible liquids or a liquid and a solid.

SFE refers to the energy stored at a solid’s surface from disrupted molecular bonds, high-SFE materials like metals, glass, and ceramics wet easily, whereas low-SFE materials such as PTFE or polypropylene resist wetting and are harder to coat or bond.

The Critical Role of Surface Tension in Battery Manufacturing & Research

Surface tension plays a critical role in battery manufacturing as it has a direct impact on the quality of the coating and material wetting which affect the overall cell performance.

Electrode Slurry and Coating: Slurries of active materials, binders, and solvents must wet copper or aluminium foils evenly. If surface tension is too high or too low, coatings can bead or form uneven layers, leading to defects and performance loss.

Electrolyte Wetting: Electrolytes must fully penetrate porous electrodes and separators for efficient ion transport. Poor wetting from a surface tension mismatch can cause dry spots, reduced capacity, and safety risks. Lower surface tension generally speeds wetting.

Performance and Safety: Surface tension impacts slurry dispersion stability, affecting how well nanoparticles and additives are distributed. Good control improves energy density, safety, and reliability.

Aqueous Processing: Moving to water-based slurries instead of toxic solvents like NMP makes surface tension control even more critical.

In short, surface tension is fundamental for achieving reliable wetting, uniform coatings, strong adhesion, and consistent material distribution, essential for high-performance, long-lasting batteries.

Key Methods for Surface Tension Measurement

Surface tension is typically measured by observing how a liquid behaves at its interface (usually with air) using methods based on mechanical force or optical analysis.

Force Tensiometry

Du Noüy Ring Method: A platinum ring is submerged in the liquid and slowly pulled upward. The force needed to detach the ring is proportional to the surface tension.
Wilhelmy Plate Method: A thin, flat plate (usually platinum) is partially immersed, and the force acting on the plate is used to calculate surface tension.

Example instrument: The KRÜSS Tensiio Force Tensiometer provides automated, precise, and reproducible measurements for liquids and solids. With an optional high-resolution camera, it can record the contact area at the liquid surface, enabling simultaneous optical drop analysis and adhesion measurement.

Optical Tensiometry:

Pendant Drop: A liquid drop is suspended from a needle and its curvature is analysed via the Young–Laplace equation.

Sessile Drop / Contact Angle: Measures the angle where a liquid, solid, and gas meet, providing insight into wettability, adhesion, and surface free energy (SFE). This is commonly performed using a Goniometer/tensiometer method, which allows precise measurement of contact angles and droplet shapes for both research and quality control applications.

Example instrument: The KRÜSS DSA100 Drop Shape Analyser measures contact angle, surface tension, and interfacial tension with high-speed cameras and advanced software. It’s ideal for optimising electrode and separator wetting, checking electrolyte compatibility, ensuring slurry coating homogeneity, and supporting QC.

Learn more about the Goniometer/tensiometer method.

Bubble Pressure Tensiometry:

A bubble forms at the end of a submerged capillary, and the pressure needed to form it reflects the surface tension at that moment. This method measures dynamic surface tension over milliseconds to seconds, valuable for electrolytes or slurries containing surfactants, dispersants, or binders.

Example instrument: The KRÜSS BPT Mobile Bubble Pressure Tensiometer captures surface tension changes in real time for rapidly changing formulations. The pressure needed to form each bubble reflects the surface tension at that exact moment. This is especially useful for formulations that change over milliseconds to seconds, such as those containing surfactants, dispersants, or binders.

Spinning Drop Tensiometer

The Spinning Drop Tensiometer is specialised for ultra-low interfacial tension, commonly used in emulsion studies. It is increasingly relevant to advanced battery systems with ionic liquids, complex liquid–liquid interfaces, and multiphase electrolytes.

Dynamic Foam Analyser

Measures foam formation, stability, and drainage—important in slurry preparation, coating, and electrolyte mixing, where unwanted foaming can cause defects.

Example instrument: The KRÜSS DFA100 evaluates foaming behaviour and anti-foaming strategies for more consistent manufacturing.

Portable contact angle instrument

Hand-held devices like the KRÜSS Mobile Surface Analyser (MSA) provide fast, on-site wettability and cleanliness checks—ideal for QC, surface preparation, and coating processes in battery production.

Matching Measurement Methods to Specific Instruments

Choosing the right analytical technology depends on the type of surface or interfacial measurement you need. Whether you’re studying wetting behaviour, optimising formulations, or characterising material interfaces, KRÜSS offers a range of precise instruments tailored to specific applications.

The table below matches measurement methods to the most appropriate KRÜSS tensiometers, helping you select the best system for your needs.

Method	What it measures	Best For	Advantages	Recommended Instrument
Du Noüy Ring	Static surface/ interfacial tension using a platinum ring	Quality control of surfactant or coating liquids	Simple, industry-standard (ASTM D 971 and IEC 62961)	KRUSS Force Tensiometer K20 (Compact, entry-level tensiometer for routine QC) Tensiio (Automated, high precision tensiometer with optional optical camera)
Wilhelmy Plate	Static surface tension, contact angle, wetting force using a thin plate	Solid–liquid wetting, adhesion testing, surface treatment	High precision, fast	KRÜSS Force Tensiometer K20 Tensiio
Pendant Drop	Surface/interfacial tension (static) using shape analysis of a hanging droplet (Young–Laplace fit)	Electrolyte–air or oil–water systems	High accuracy, low sample volume, temperature and atmosphere control	KRÜSS Drop Shape Analyser DSA100 (Automated, high precision, modular system ideal for challenging surfaces) DSA 30 (Ideal for labs needing reliable measurements with some flexibility, without full automation or advanced modules) DSA 25 (Great for teaching labs, routine quality checks, or first-step research projects with budget constraints)
Sessile Drop / Contact Angle	Static contact angle, surface free energy (SFE) using a drop placed on solid to assess wetting & adhesion	Wetting, surface treatment, coatings, battery electrode & separator surfaces	Wetting and adhesion data together	KRÜSS Drop Shape Analyser DSA100 DSA 30 DSA 25
Bubble Pressure	Dynamic surface tension using the maximum pressure to form a gas bubble in liquid	Surfactant screening, slurry formulation, battery slurries	Millisecond time resolution	KRÜSS Bubble Pressure Tensiometer BP100

Integrating Surface Tension Measurement into Battery R&D and QC

From lithium-ion to solid-state and sodium-ion, battery technology is advancing rapidly, but one principle applies to them all: consistent interaction between materials drives performance. Achieving optimal wettability of electrodes and separators by the electrolyte boosts capacity, safety, and lifespan.

By integrating surface tension measurement into both R&D and QC, manufacturers can prevent costly defects and ensure product consistency from the lab to the production line. Learn more about integrating analytical techniques into battery recycling.

Holistic approach: Combine force tensiometry for electrolyte behaviour with contact angle measurements for electrode surfaces to gain a complete interfacial profile.
From lab to line: Apply these measurements to verify slurry stability, electrolyte compatibility, and coating quality at every stage.
Future-ready automation: ATA Scientific supplies KRÜSS instruments with modular accessories and high-throughput features such as Liquid Needle and Multi-Dosing Systems—ideal for streamlined, standardised testing in modern battery production.

Measuring surface tension doesn’t have to be complicated

Measuring surface tension is simpler than you might think, especially with the right tools. In battery research and manufacturing, mastering surface tension is not just a technical detail; it’s a performance driver. The way liquids wet, coat, and interact at interfaces directly shapes battery efficiency, safety, and lifespan.

With KRÜSS instruments from ATA Scientific, you can measure surface tension, contact angles, and surface free energy with precision and repeatability. Whether you need a portable device for quick QC checks or a fully automated analyser for advanced R&D, our modular systems are built for accuracy, consistency, and high-throughput workflows.

When you integrate these capabilities into your process, you’re not just collecting data—you’re accelerating innovation, optimising material compatibility, and boosting overall battery performance.

Bottom line: Accurate surface tension measurement is essential for building high-performance, reliable, and safe batteries.

Talk to ATA Scientific today for expert guidance and a hands-on demo—see how KRÜSS technology can optimise your battery R&D and production.

Sources:

Tensiometers like the KRUSS tensiometers measure the surface tension of fluids to give you a better understanding of their interfacial behaviour.

How exactly does a tensiometer measure surface tension? There are a number of different tensiometer types, each with their own unique method of calculating surface tension.

What is a tensiometer?

At its most basic, a tensiometer is an instrument used to measure the surface tension of liquids. This can include:

liquid coatings
liquid adhesives
liquid lacquers

In practical application, they help scientists predict and develop the behaviour of a whole host of products, including cleaning agents industrial parts cleaning, electroplating processes, measure soil moisture, and the wettability, absorption and density of powders.

What is surface tension?

Surface tension is the tendency for fluid surfaces to display an elastic behaviour, acquiring the smallest surface area possible. Think about a pool of liquid on a bench.

Why does it tend to bunch together?
Why does the exterior of the mass look like it is bonded by an elastic band?

To answer these questions we must first understand how fluid molecules behave.

The relationship between water and air

At the interface of two molecular masses – fluids, solids or gasses – a lot can happen. The molecules at the interface tend to be more attracted towards their own molecules. This is what gives fluids “shape”. It’s also why they tend to be the smallest size possible, as the molecules at the interface are pulled ‘inwards’.

This is easy to demonstrate with water, a liquid with a higher surface tension than most other fluids. Where water meets air, water molecules have a higher attraction to each other than the air molecules. We see water molecules at the interface of air and water resistant to air and attracted to other water molecules.

Cohesion and adhesion

The two principles at play in all interfacial tensions are cohesion and adhesion:

Cohesion: Referring to the attraction of molecules of the same kind, this force is responsible for giving fluids their shape. In a mass of water molecules, all molecules are attracted equally to neighbouring water molecules. At the edge or surface, where there are no fluid molecules on one side, there is more ‘pull’ towards the centre, resulting in an inward pressure.
Adhesion: Adhesion is a similar principle, but defines how molecules from different substances attract to one another, such as the adhesion of water molecules to a glass test tube leading to an upward turning meniscus and contributing to capillary action .

The end result is that there is an inward force on the fluid surface that causes the water to behave as if their was an invisible elastic membrane around the water. This imbalance of tensions is where we get the name “interfacial tension”.

What is interfacial tension?

Interfacial tension means practically the same thing as surface tension. The main difference is that surface tension refers to a single liquid surface, where interfacial tension refers to the interface of two immiscible liquids, solids or gases.

Tip: Surface tension is a subset of interfacial tension where the force exerted by the second surface is zero.

Types of tensiometers

Now that you understand surface tension, let’s look at how you can measure it using a tensiometer.

There are several different types of tensiometer, each measuring the surface tension of a fluid in a distinct way. The best method to use depends on the volume, viscosity, and availability of the fluid.

Contact Angle Goniometer/ tensiometer

The Goniometer is most commonly used to measure the surface tension and interfacial tension of expensive liquids, as it only requires a few drops to get a reading.

Using either the pendant or sessile drop methods, drops of fluid are captured by the Charge-Coupled Device camera, a device used to capture the movement of electrical charge.

The digital image of the charge is processed through computer software using the Young-Laplace equation, which describes the capillary pressure difference at the interface between two fluids.

Wilhelmy Plate tensiometer

The simplest and most accurate form of tensiometer, the Wilhelmy Plate only requires a plate to make contact with a liquid to provide a result. The plate is usually made from filter paper, glass or platinum. In truth, it doesn’t matter what the plate is made from as long as the material can be ‘wetted’ by the fluid. The measurement is of the force exerted on the plate. Because the plate doesn’t move, it is generally a highly accurate measurement.

Du Noüy-Padday method tensiometer

The Du Noüy-Padday method works by dipping a rod in and out of a pool of liquid and measuring the precise force used to extract the rod from the fluid. The main advantages of this method are that it is repeatable and accurate even on fluids with high viscosity. The main drawback is that it requires a pool of fluid so it might not be realistic for expensive liquids.

Du Noüy Ring tensiometer

Similar to the above method, only the Du Noüy Ring tensiometer uses a platinum ring which is submersed and held horizontally in liquid and then pulled out. The ring has to be almost exactly perfect. Any scratches or damage to the ring material can alter the ring significantly.

Bubble pressure tensiometer

By pumping a gas stream into a capillary that is immersed in fluid, this tensiometer is able to measure surface tension through the behaviour expected by bubbles forming at the tip of the capillary.

Recommended tensiometers

The KRUSS tensiometers are among the most accurate devices for measuring static surface tension and interfacial tension of fluids.

Using the tensiometry principal, the Attension range tensiometers measure:

surface and interfacial tension
critical micelle concentration
dynamic contact angle
surface free energy
powder wettability
density

Take your research and development to the next level with accurate measuring tools at cost-effective price points. Contact ATA Scientific to find out more about our preferred scientific instruments today.

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How to Measure Surface Tension for High-Performance Battery Manufacturing