What you can measure

  • Interfacial dilatational rheology
    Pulsating drop method
  • Surface- and interfacial tension
    Pendant drop and reverse pendant drop methods
  • Static contact angle
    Sessile drop, captive bubble, and meniscus methods
  • Surface free energy 
    Sessile drop, captive bubble, and meniscus methods
  • Dynamic contact angle
    Dynamic contact angle, advancing and receding contact angle, contact angle hysteresis, and roll-off angle
  • Roughness-corrected contact angle and 3D surface roughness 
    Fringe projection phase shifting method

A quick view

This 1-minute video will give you an overview of interfacial viscoelasticity measurements with Theta Pulsating Drop. Move to full screen for the best experience. 

3 reasons to invest

Interfacial viscoelasticity with ease

Fully automatic measurements of interfacial viscosity and elasticity are user-independable and highly accurate due to automatic droplet creating and pulsation as well as due to high end imaging system.

Smarter rheology measurements

Automatic evaporation compensation keeps the droplet volume stable. Wide pulsation frequency range up to 10 Hz with reliable piezo technology. Sinusoidal, triangle, and square waveforms for wide possibilities. Temperature control option up to 250 C. 

Widen your possibilities

In addition to interfacial rheology, the same system is ready for surface tension, interfacial tension, contact angle and surface free energy measurements. Handle your current and future surface science needs at once. 


Attension Theta Flex

An award-winning instrument

Did you know that Attension Theta Flex received a Red Dot for its ground-breaking  and intuitive design? Our instrument was elected Best of the best in the category of Industrial design at the Red Dot Award for Product Design 2020, making it a winner in the world’s most renowned design competition. 

Statement by the jury
"This optical measuring instrument for determining surface tension offers an outstandingly user-friendly and extremely precise manner of interaction. Markings with blue accent colour ensure good user guidance, while the differently sized thumb screws allow different parts to be set precisely. In addition, Theta Flex also impresses with its highly practical modular structure. This enables the instrument to be used cost-effectively in both research and industrial areas of application."

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A closer look

Theta Pulsating Drop is based on the extremely versatile Theta Flex optical tensiometer which is characterized by its versatility, reliability and automation. Check out the system specifications below. 

Theta Flex

Available Measurements

Static contact angle
Dynamic contact angle
Surface/Interfacial tension
3D surface roughness
Interfacial rheology
Surface free energy
Zisman Plot, OWRK/Extended Fowkes, van Oss Acid-Base, Wu, Neumann’s Equation of State, Schultz 1 and 2

Available Measurement Methods

Sessile drop
Batch sessile drop
Captive bubble
Pendant drop
Reverse pendant drop
Dynamic contact angle
Pulsating drop
3D Topography


Measuring range (°, mN/m)
0…180, 0.01…2000
Accuracy (°, mN/m)
±0.1, ±0.01
Maximum sample size (mm)
Unlimited×100×320 (with stage)
Integrated sample holders
Frame interval
0.33 ms ... 1000 s
Maximum resolution (px)
Maximum measuring speed (fps)
USB 3.0 digital camera with zoom
Camera protection
Inside instrument covers
Camera view angle (°)
 -4.5 ... 2.5
Light source and size
LED based background lighting, 62 x 62 mm
Field of view (Ø, mm)
Measurement indicator LED
Disposable tip dispensing
Dimensions — Basic frame (L×W×H, mm)
 765 x 230 x 435 
Weight — Basic frame (kg)
Power supply (VAC)
Frequency (Hz)
Droplet placement
Sample stage
Possible upgrades
Theta Flex Auto 5
Auto, 4 liquids Auto Auto XYZ 1984 × 1264 px, max 3009 FPS Full
Theta Flex Auto 4
Auto, 2 liquids Auto Auto XYZ 1984 × 1264 px, max 3009 FPS Full
Theta Flex Auto 3
Auto, 1 liquid Auto Auto XYZ 1984 × 1264 px, max 3009 FPS Full
Theta Flex Auto 2
Auto, 2 liquids Auto Auto X, Manual YZ 1984 × 1264 px, max 3009 FPS Full
Theta Flex Auto 1 
Auto, 1 liquid Auto Manual XYZ 1984 × 1264 px, max 3009 FPS Full
Theta Flex Plus
Auto, 1 liquid Manual Manual XYZ 1984 × 1264 px, max 3009 FPS Full
Theta Flex Basic
Manual Manual Manual XYZ 1984 × 1264 px,  max 3009 FPS Full


OneAttension Software

OneAttension software is a fine combination of a very intuitive interface and high functionality. Follow your experiment live and get the results within seconds. Let's have a look at the features!  


OneAttension Features

  • Automatic droplet creation, pulsation and shape analysis 
    Less user-dependency, more accuracy
  • Autonomous measurements
    Set up the desired measurement parameters and the entire measurement will run automatically
  • Versatile pulsation features 
    Sinusoidal, triangle, and square waveforms. Adjustable frequency, amplitude, recording time, and settle time
  • Results always available 
    Reanalyze the results as many times as you wish. Plotting, exporting, comparing, and reporting all included 
  • User-friendly interface 
    To get you going in no time  
  • Comes with full capabilities 
    Every measurement mode included from interfacial rheology to interfacial tension and contact angle    


Add more possibilities

Have a look at a few of the additional modules that can be used for added capabilities. You can find the full range of accessories below.  


Measuring Chamber, electrically heated, 250° C

Thermostatted electrically heated measuring chamber for temperature control up to 250 C. 


Topography 3D module

The unique 3D Topography module takes the wettability and adhesion analysis into a completely new level by measuring both contact angle and surface roughness of the sample in a single measurement. Distinguish the effect of roughness on contact angle and surface free energy. 


High Pressure Chamber

The High Pressure Chamber is designed for wettability research within enhanced oil recovery and enables measurements at pressures up to 400 bars and temperatures up to 200°C. Integrated chamber piston and sample port are optimized for the best usability and versatility. 


Tilting Cradle

A software controlled tilting cradle. Used for studying dynamic contact angles. Tilting range from 0 to 90° and tilting resolution 0.1°. 


Picoliter Dispenser

Automated picoliter-scale drop formation. Especially for inkjet applications and for measuring contact angle on very small sample areas.


What others say

Our instruments are present at many prestigious universities and research facilities world wide. Take a minute to find out what others say about Theta Flex. 



Dr. Nicola J. Irwin. Queen’s University Belfast

"The ability to accurately measure contact angle as a measure of surface wettability is of utmost importance as we develop new technologies to prevent medical device-associated issues of infection and tissue trauma. The ease-of-use of the instrument and associated software is a major advantage and the support offered by the team, particularly with new applications, is exceptional.”

Queens Univeristy Belfast

Queen’s University Belfast

This prestigious university in Northern Ireland is ranked amongst the top 200 in the world. Dr. Nicola J. Irwin, Lecturer in Pharmaceutical Materials Science School of Pharmacy, has been using our instrument in her work. 



Ville Jokinen. Aalto University

"The ability to measure the advancing and receding contact angles with a single click and having the data into a convenient format saves time and reduces the human error."

Watch the full story



Aalto University, Finland

Aalto University is a top Finnish university combining science, technology and arts into a collaborative environment for both scientific communities and companies. Our contact angle meters and tensiometers have been used there in research for decades. 




Researcher at MIT

“The reproducibility of the measurements acquired is excellent even with the lowest surface energy values and the tensiometers are quite flexible with regards to sample size. The software is also very useful and the customer support for the products is excellent.”



MIT, Massachusetts Institute of Technology, is a world-leading research university with a mission to advance knowledge and educate students in science and technology. MIT use our tensiometers to study contact angles and interfacial energy. 


Learn more

We have gathered all our in-depth knowledge associated with Theta Pulsating Drop. Browse around amongst webinars, case studies and white papers to find a topic of interest. 

  • Attension

How to Measure Quality of Transformer Oils

Learn more about transformer oil testing using interfacial tension measurements and the available standards.

Go there

Interfacial Rheology: From Fundamentals to Application

Let Professor Gerald G. Fuller take your knowledge on interfacial rheology to the next level.

Go there
  • Attension
White Paper

Surface and Interfacial Tension

Learn what it is and read our review of the most commonly used measurement techniques.

  • Attension

Comparison of ASTM D971 and IEC 62961 Standards

Find out the differences between the standards for measuring the quality of the insulating oils used for electrical transducers.

Go there
  • Attension

Effect of Temperature and Pressure on Wettability of Solids

Listen to Professor Zhenghe Xu sharing his knowledge on bitumen recovery.

Go there
  • Attension

The Importance of Surface Tension in Industry

Detergents, paints, food. We give you examples to how surface and interfacial tension measurements are utilized in different industries.

Get it
  • Attension
White Paper

Surface and Interfacial Tension

Study the different measurement methods to select the best choice for your application.

  • Attension

Why Interfacial Rheology is Important

Get examples on why interfacial rheology is important in various industries.

Get it
  • Attension

Surface Tension and Surfactants in Industrial Processes

Get an overview of how surfactants are used in industrial processes.

Go there
  • Attension

Critical Micelle Concentration - What is it and how to measure it?

Learn more about critical micelle concentration and how it can be measured with surface tension measurements

Get it
  • Attension
Case Study

Interfacial Rheology as Emulsion and Foam Stability Indicator

Shows how interfacial rheology measurement can be used as quality control tool.

Get it