Optical tensiometer for simple and accurate measurements of contact angle

  • Theta Optical Tensiometer
  • Theta Lite Optical Tensiometer
  • Theta QC Portable Contact Angle Meter

Typical Applications using Contact Angle

Taking measurements of contact angles, surface tension or interfacial tension gives information on a range of material properties e.g.  absorption, adsorption, cleanliness, interfacial rheology, spreading, surface free energy, surface heterogeneity and wettability. It is these properties that are vital in studying and developing or controlling the quality of engineered surfaces and technical liquids.  Extremely accurate and versatile, optical tensiometry is an advanced technique used to characterise both solids and liquids in virtually any industry or research area. With applications ranging from the surface properties of contact lenses to the quality control of semiconductors.

 Operating principle

Optical tensiometers record and automatically analyse the shape of drop images over time. The shape of the drop is a function of the surface tension of the liquid, surface free energy of the solid, gravity and any density difference between sample liquid and surrounding medium. On a solid the drop shape and the contact angle depend on the solid’s surface free energy. The captured image is analysed with a drop profile fitting method to determine the contact angle and thus surface tension/surface energy.

INSTRUMENTS
Theta

Theta is an advanced optical tensiometer for high accuracy and easy measurement of absorption, adsorption, cleanliness, contact angles, interfacial rheology, interfacial tension, spreading, surface free energy, surface heterogeneity, surface tension and wettability. Theta harnesses the power of full automation to deliver best-in-class performance for R&D, quality control and process control.

Theta measures static and dynamic contact angles, static and semi-dynamic surface/interfacial tension, surface free energy and drop volume. A range of drop profiles are analysed i.e. sessile drop, pendant drop, receding contact angle, advancing contact angle, tilting drop, captive bubble, meniscus and reverse pendant drop. 

Precision, robustness and intuitive user experience are built-in. All you need to do is select the level of automation and advanced functionality you need. Theta quality camera and optics are enhanced by a 6.5x zoom lens enabling characterisation of very small drops. The open design and large frame are appropriate for large samples. With optional motorised sample stage, motorised vertical movement and a dispenser Theta can function in a fully automated mode, placing drops in predetermined locations on the substrate and measuring the contact angles.

Theta Lite

Theta Lite is a compact and robust optical tensiometer for simple and accurate measurements of contact angle and surface free energy. It enables the study of a number of material properties such as absorption, adsorption, cleanliness, spreading, surface heterogeneity and wetting.  Theta Lite measures contact angles, surface free energy and drop volume. The available drop profiles are: sessile drop, pendant drop, captive bubble, meniscus and reverse pendant drop. As standard the Theta Lite comes equipped with manual sample stage and liquid dispenser, making it a convenient and cost-effective instrument for research, industrial processes and educational use.

Choosing the extended software option converts Theta Lite into a more versatile instrument by adding measurement mode, data storage and data analysis capabilities e.g. static and semi-dynamic surface tension can be measured.  In addition pendant drop, reverse pendant drop and meniscus drop profiles are available with the extended software.

Theta QC

Theta QC Optical Tensiometer is a mobile contact angle meter enabling characterization of solid surfaces and liquid-solid interactions.  It is primarily used for quality control measurement and characterization of large objects.

Theta QC deposits droplets from its integrated dispensing syringe which can be easily filled with your desired liquid. The drop can be visualized from the Viewfinder for accurate placement of the drop onto the solid sample. Following deposition, a picture of the drop is taken. It is possible to set a delay between the drop deposition and the recording. Theta QC analyzes the drop shape and calculates the contact angles formed between the liquid and the solid using the Young-Laplace equation, a standard in tensiometry. The right contact angle, left contact angle and average contact angle are displayed on the screen. Data is saved in the instrument. Measurement data can be transferred wirelessly (WLAN) or via a cable connection to an external computer where the Theta QC Data Receiver Software is installed.  

For further details on the Theta QC please click here


Technical specification - Theta & Theta Lite

  Theta Theta Lite
Available Measurements    
Static contact angle Yes Yes
Dynamic contact angle Yes  
Surface/interfacial tension Yes With extended software option.
Intefacial rheology Yes  
Drop volume Yes With extended software option.
Surface free energy Zisman Plot, Owens-Wendt-Rabel, Simple Fowkes, Extended Fowkes, van Oss Acid-Base, Wu, Neumann’s Equation of State, Schultz 1, Schultz 2.

Available Drop Profiles

    
Sessile drop Yes Yes
Captive bubble Yes Yes
Pendant drop Yes With extended software option.
Reverse pendant drop Yes With extended software option.
Meniscus Yes With extended software option.
Receding contact angle Yes  
Advancing contact angle Yes  
Tilting drop Yes  
     

Click to read our eBook: Surface Energy Testing

For further technical specifications please open pdf below.

 

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