Curtin University: Measuring Contact Angle and Wetting Properties

This report delves into the measurement of contact angles and wetting properties, crucial in various industrial processes. It discusses techniques like the telescope-goniometer method, drop-shape analysis, and the Wilhelmy balance method, highlighting their applications and limitations. The study also explores ultra-small droplets on solid surfaces, testing wetting theories at the manometer scale to provide insights into contact angle phenomena and wetting behavior. The analysis includes graphical representations of temperature and contact angle variations over time, emphasizing the relationship between these parameters and wettability. The report concludes that temperature and contact time are key determinants of a solid's wettability, with heat transfer and fluid flow calculations offering further analytical guidance. References to relevant works by Mittal and Bracco support the findings and methodologies discussed.

Measurement of Contact Angle and Wetting Properties
John A. STUDENT, B. Supervisor* and C. Staff
Department of Mechanical Engineering, Curtin University, Perth, WA 6845, Australia
*Company Name, Company Address
E-mail: [e-mail]
ABSTRACT
This study is on the various techniques that are mostly usable in the measurements of the contact
angles among them the conversational telescope-goniometer method, the drop-shape analysis methods
that were recently developed and the Wilhemy balance method. Elaborate applications and limitations
of each of the methods are described. Concern is also attached to exploration on ultra-small droplets
on solid surfaces allowing the testing of the wetting theories down to the manometer scale. This brings
new insights into the phenomena of contact angle and wetting behaviour.
INTRODUCTION
The topic wetting has attracted a lot of interest and attention both from the applied and fundamental
perceptions due to its numerous applications in the industrial processes. Wettability studies include
taking measurements of contact angles as the primary data which is illustrative of the extent of
wetting when a solid comes into contacts with a liquid. Large contact angles mean low wettability
while small contact angles mean high wettability1. The fundamentals of the basic science behind
wetting and contact angle is given an in depth discussion in this chapter as well as an elaborate
discussion on the different techniques used in measuring angles. Direct and indirect force methods are
the most common classifications of the techniques. Calculations are done based on the values of
contact angle-the surface tension of the solid, which is used in the determination of the wetting
characteristics of the solid.
RESULTS AND DISCUSSION
The first graph was an illustration of how temperature changes with changes in the length of time for
the two thermocouples: left and right thermocouples. Another graph introduced is one on the average
temperature of the surface2. As can be observed from the graphs, the temperature increases with an
increase in the length of the time. As time increases, the thermocouples gains more kinetic energy in
its particles thereby leading to increased rate of vibration of the particles and hence an increase in the
temperature with time.

Figure 1: Graph of Temperature against time
Contact angle decreases with an increase in temperature as illustrated in the graph above and increases
with a decrease in the temperature. The Navier-Stokes equation is used in describing the flow of the
fluid in the liquid droplet while the energy equation is used in the description of the heat transfer in
the liquid droplet in the solid substrate. Partially wet droplets have neglible influence on the contact
angle which is relatively higher in highly wetting and non-wetting droplets of liquids2.
Figure 2: Graph of Contact Angle against Temperature

Figure 3: Graph of Contact Angle against Time
Closely related to contact angle is time as is observed in the above graph. A longer time translates to
lower or less contact angle which is maximum at minimum time. Important to remember at this point
which minimum contact time is, the temperature is very low which facilitates or enhances high
contact angles1. At low temperature, the contact angle is increased which translates to low wettability
as contact be observed from the graphical illustrations.
CONCLUSIONS
The measure of the contact time is primary is determining the wettability characteristic of a solid with
a liquid. Temperature and contact time are among the key parameters which must be taken into
account when determining the wettability characteristics of any solid with a liquid. Calculations on the
heat transfer and the flow of the fluid provide a guide on further analysis of these wettability
characteristics.
REFERENCES
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[1] K. L. Mittal, Advances in Contact Angle, Wettability and Adhesion, 3rd ed., K. L. Mittal, Ed. New
York, USA: Wiley, 2013.
[2] Gianangelo Bracco, Surface Science Techniques, 4th ed., Gianangelo Bracco, Ed. London, UK:
Springer Science & Business Media, 2013.
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