1. 界面科学測器の協和界面科学
  2. Kyowa Interface Science
  3. Interface Science
  4. What is Contact Angle?

What is Contact Angle?

What is Contact Angle?_1
Infiltration Rate method_3
Infiltration Rate method_4

θ/2 method

Measurement of the static contact angle_1
Measurement of the static contact angle_2

Tangent method

Tangent method

Curve fitting method

Sessile Drop method in a function of time

Extension/Contraction method

Extension/Contraction method

Sliding method – measurement on a slope

θa:  Advancing angle
θr:  Receding angle
α:   Sliding angle
The equation of the adhesive energy:
E:  Adhesive energy
r:   Radius of the droplet
m:  Mass of the droplet
g:   Acceleration of gravity
α:  Sliding angle

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DMo series

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DMo-WA series

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DMs-401

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Wilhelmy method

Wilhelmy method_1
Wilhelmy method_2

F…Forces acting on the solid (measured)
γ…The surface tension of the liquid (must be known in the case of contact angle measurements)
L…The circumference of the solid sample perimeter (must be known)
θ…The contact angle of the liquid with the solid (assumed to be 0º)
S…The cross-sectional area of the solid sample distance
h…The Immersion depth of the solid sample
ρ…The density of the liquid sample
g…The gravitational acceleration

Wilhelmy method_3

A solid sample is suspended from the balance and immersed in the liquid. Raising the stage will immerse the solid sample deeper into the liquid, and the advancing contact angle θA can be measured. Lowering the stage will pull the solid out of the liquid, and the receding contact angle θR can be measured.

The more the solid sample is immersed in the liquid, the more the buoyant force increases, causing the force acting on the balance to decrease. Therefore, for both the advancing contact angle θA and the receding contact angle θR, the obtained weight curves (see the figure on the right) must be determined through linear regression, and the wetting forces have to be extrapolated to zero-depth immersion.

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Infiltration Rate method

Infiltration Rate method_1 

l… Height of the liquid front
t… Time
r… Capillary radius of the compressed powder
γ… Surface tension of the liquid
η… Viscosity of the liquid
θ… Contact angle

Infiltration Rate method_2

In the actual measurement, a liquid sample is infiltrated into a column filled with powder, and the change in the weight W is tracked for the elapsed time t. Ideally, the linear relationship is obtained by plotting t for W2. The contact angle and infiltration rate are calculated from the slope of this line. In addition, in order to calculate the contact angle, the powder-filled capillary radius value is required besides the values of liquid surface tension and viscosity. That capillary radius value is determined experimentally by measuring the sufficiently wet liquid for the powder and regarding the contact angle as 0º.

Infiltration Rate method_3
Infiltration Rate method_4

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DY-700/500

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