Analysis software FAMAS
The analysis software FAMAS is an integrated software package used with KYOWA’s contact angle meters and dynamic surface tensiometer BP series. The following features are part of the software:
Sessile drop method
Typical contact angle measurement of droplets on a leveled surface. Measurements in static and dynamic modes in the time function are available.
Sessile drop method as a function of time
Sequential measurements of the contact angle at a certain time interval. 30 and 60 fps camera systems are available, depending on the model, and an optional high-speed capture system up to 2,700 fps is also available.
Typical applications: Initial spreading, absorption properties, and the effect of surface-active agents on wetting behavior.
Extension/contraction method
The extension/contraction method, also known as the captive drop method, is a dynamic method for measuring the advancing and receding contact angles. As the droplet volume captured by the needle on the solid surface increases or decreases, the advancing angle is measured during wetting as the liquid moves forward. On the other hand, the receding angle forms during dewetting as the liquid retreats.
The contact angle hysteresis, which is the difference between advancing and receding angles, is affected by surface adhesion, surface roughness, and the surface's chemical heterogeneity.
An automatic dispenser system that maintains a constant flow rate for high reproducibility is highly recommended for reliable results.
Sliding method
The sliding method, also called the tilting method or roll-off method, involves measuring advancing and receding angles while an external tilting stage tilts the instrument up to 90 degrees. The angle at which a droplet begins to slide or roll off a solid surface is called the sliding angle.
Simultaneously, the adhesive energy between the droplet and the solid surface is analyzed. Since adhesive energy is independent of droplet volume, it can serve as a comparative metric for liquid samples of varying sizes.
To perform roll-off angle measurements, a sliding kit that includes an external tilting stage and FAMAS software add-on is required.
Typical applications: Repellency/hydrophobicity of hydrophobic surface such as self-cleaning coatings, Characterization of droplet hysteresis
Dynamic sliding method
The basic idea is the aforementioned sliding method, but this method focuses on the roll-off speed and acceleration of a droplet sliding off an inclined surface to observe hydrophobic and oleophobic properties in more detail.
Three-state method
Contact angle measurements typically measure the wettability of a solid by a liquid in a gaseous phase. The three-state method, however, measures the contact angle of a liquid or an air bubble in a surrounding bulk liquid phase.
Kyowa offers a special kit that includes a glass cuvette, sample stages, special needles, and magnets.
Figure 1 illustrates the measurement of a liquid droplet with a higher density than the bulk liquid phase. In contrast, Figure 2 shows an air bubble or a liquid droplet with a lower density than the bulk phase. Here, an inverted needle deposits an air bubble or droplet beneath the solid sample.
Figure 1 – Set up for denser probe phase in a lighter bulk phase
Figure 2 – Set up for lighter probe phase in a denser bulk phase
Algorithms of contact angle analysis
The analysis software FAMAS offers several analysis algorithm methods that can be selected to determine the contact angle of a specific droplet under certain conditions, such as droplet size, symmetry, and contact angle range:
- Height-width method
Determines the contact angle from the droplet's image height and diameter
- Tangent method
Determines the tangent line using three endpoints close to each three-phase point of the droplet's image
- Circle fitting
Calculates the contact angle by fitting a theoretical curve of a partial circle to the silhouette of the droplet
- Ellipse fitting
Calculates the contact angle by fitting a theoretical curve of a partial ellipse to the silhouette of the droplet
- Young-Laplace fitting
Calculates the contact angle by fitting a theoretical curve calculated from the Young-Laplace equation to the silhouette of the droplet
Surface free energy analysis of solids
The software determines the surface free energy of solids and their components from contact angle measurements with at least two different liquids, each with known dispersive and polar components, such as water and diiodomethane. Different models for determining the surface free energy of solids, such as the Owens-Wendt-Rable-Kaelble, geometric mean, harmonic mean, acid-base interaction analysis (work of adhesion, interfacial free energy), Young-Dupré, and the Zisman plot, are available.
The surface energy kit, consisting of a set of needles and various chemicals, is recommended for quick, easy analysis of surface free energy.
Applications
- Adhesive Properties
Bond strengths, adhesion failures
- Surface Modification
Determination of surface characteristics, such as the polarity of solids, pre- and post-surface treatment
- Hydrophilicity/Hydrophobicity
Evaluating surface engineering for functional (smart) surfaces
Features
- Standard Deviation
Reflection of the contact angle measurement standard deviation in surface free energy calculations for reliable, statistically significant results
- Residual Value
Elimination of imaginary numbers arising from the analysis of hydrophobic surfaces by recalculating and subsequently adjusting them, and indicating the residual value, as a reference for the uncertainty in the surface components
Surface and interfacial tension of liquids
The pendant drop method enables the measurement of surface and interfacial tension of liquids using Young-Laplace or ds/de algorithms. The pendant drop method has advantages in the following points compared to the conventional Wilhelmy plate and du Noüy ring method:
- Volume
Measurements only need a few uL of liquid
- Temperature
Temperature can be controlled up to 400℃, enabling measurements of waxes and molten polymers
- Time
Due to its short-term exposure to air, it is suitable for liquids with rapidly changing surface tension
Automatic recognition of droplet deposition
The analysis software automatically detects when a droplet is deposited from a needle onto a solid surface, and the user can set a time delay between the droplet deposition and the start of measurement. This is particularly useful for liquid samples that quickly spread on a solid surface, leading to a rapid initial change in contact angles.
Focusing Aid and Droplet Volume Monitoring
- Focusing Aid
The focus level indicator features a bar chart and two numerical values that show the highest and current focus levels on the live monitor, helping you adjust the focus quickly and easily.
- Droplet Volume Monitoring
The software constantly calculates the actual droplet volume and displays it on the image monitor. When using an automatic dispenser, the software controls the droplet volume according to the preset value.
Display of data
Measurement results, as well as the average and standard deviation of each row of data, are displayed in spreadsheet-like measurement sheets with 45x10 (RxC) cells.
- Extensive Data
In addition to the contact angle, the FAMAS software collects data on droplet volume, height, width, absorbance, etc.
- Charts
Different charts, such as contact angle or sessile drop volume vs. elapsed time, can be generated when the time function mode is selected.
T-test
The t-test is available for contact angle measurements using the standard sessile drop method and for interfacial tension measurements with the standard pendant drop method.
The results of the "Welch's t-test" will be shown to determine whether there is a significant difference in the measured data.
Pixel calibration
The droplet calibration standard for the standard view is a basic accessory for all models. It is made of soda-lime glass bearing one full circle for calibration and three droplet silhouettes of 5º, 60º, and 108º for periodic inspections of measurement accuracy.
With this tool, users can easily perform routine maintenance to ensure the reliability of their measurements over long periods.
A droplet calibration standard for calibration of the camera's wide-view settings, as well as pendant drop calibration standards for standard and wide-view settings, can be obtained optionally. Certificates of accuracy for the full-circle and droplet silhouettes can also be obtained.
Figure 1 shows the calibration window with a view of the 3mm calibration circle for the standard view mode, whereas Figure 2 shows an actual test measurement of the 60º silhouette using the height-width analysis method.
Figure 1 – 3 mm calibration circle for pixel calibration
Figure 2 – 60º silhouette for periodic inspection of measurement accuracy
Other functions
- Movie converter
Converts the time-function measurement images to the MPEG or AVI movie format.
- Threshold level adjustment
Helps to optimize the image analysis. Both the relative and absolute level adjustments are possible.
- Data correction on convex surfaces
The contact angles on convex surfaces, such as lenses and cross-sectioned tubes, can be corrected by simply entering the substrate's radius or by measuring the curvature directly in the FAMAS software.