Contact Angle Meter
WEISTRON Contact Angle Meter for highly accurate and easy measurements of:
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Contact angles
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Wettability
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Surface tension
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Interfacial tension
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Surface free energy
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Absorption
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Adsorption
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Spreading
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Cleanliness
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Surface heterogeneity
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Interfacial rheology
These properties are vital in studying and developing for controlling the quality of engineered surfaces and technical liquids. With applications ranging from the surface properties of contact lenses to the quality control of semiconductors.
Technical Description :
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Temperature control
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Continuously programmable measurements
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Programmable customized syringe pump(s)
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Built-in computer systems (with Microsoft Windows)
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Built-in Software Interface for Collecting and Analyzing Data
System Description ( Model: CA1100 ):
1. Dosing System / Syringe Pump System
1-1. Manual Dosing Unit
1-2. Programmable Syringe Pumps (optional)
1-3. Customer can purchase arbitrary sets of syringe pumps according to their need. Each syringe pump can work independently. Users can set the speed of the pump on the embedded control computer. (optional)
2. Sample Stage System
2-1. Stage Platform
2-2. Tilting Stage (optional)
2-3. Temperature Control System (optional)
2-4. Environmental Control System (optional)
3. Imaging System
3-1. CMOS Camera
3-2. High resolution and high speed camera (optional)
3-3. Top view video system (optional)
4. Control System
4-1. Built-in computer systems (with Microsoft Windows)
4-2. Software Interface for Collecting and Analyzing Data
4-3. Programmable customized syringe pump(s) (optional)
4-4. Continuously programmable measurements (optional)
5. Others
5-1. LCD Monitor
5-2. Keyboard and Mouse
Contact Angle
The contact angle is the angle at which the three-phase boundary liquid/solid/air interface intersect. When a liquid droplet is set onto a smooth homogeneous horizontal surface, it may spread out over substrate and the contact angle will approach zero if complete wetting takes place. Conversely, if wetting is very small, a spherical droplet is formed and the resulting contact angle reaches 180 degree. The smaller the contact angle, the greater the surface wettability or surface energy. Contact angle is a good measure of surface wettability.
Contact Angle Measurements
Contact angles can be divided into static and dynamic angles:
1. Static Contact Angles
Static contact angles are measured when droplet is standing on the surface and the three-phase boundary is not moving. A droplet is placed on the solid surface and the image of the drop is recorded. Static contact angle is then defined by fitting Young-Laplace equation around the droplet, although other fitting methods such as circle and polynomial can also be used. Static contact angles are utilized in quality control and in research and product development.
2. Dynamic Contact Angles
When the three-phase boundary is moving, dynamic contact angles can be measured. Contact angle hysteresis is the difference between the advancing and receding contact angles. Contact angle hysteresis arises from the chemical and topographical heterogeneity of the surface, solution impurities absorbing on the surface, or swelling, rearrangement or alteration of the surface by the solvent. Dynamic contact angles give the maximum and minimum values of the static contact angle. Dynamic contact angles can be measured by using two different approaches: changing the volume of the droplet or by using tilting cradle.
(1) The principle of the volume changing method:
In short, a small droplet is first formed and placed on the surface. The needle is then brought close to the surface and the volume of the droplet is gradually increased while recording at the same time. This will give the advancing contact angle. The receding angle is measured the same way but this time, the volume of the droplet is gradually decreased.
(2) The principle of the tilting cradle method:
The droplet is placed on the substrate, which is then gradually tilted. The advancing angle is measured at the front of the droplet just before the droplet starts to move. The receding contact angle is measured at the back of the droplet, at same time point.
Contact angle, Ɵ, is a quantitative measure of wetting of a solid by a liquid. It is defined geometrically as the angle formed by a liquid at the three-phase boundary where a liquid, gas and solid intersect. The well-known Young equation describes the balance at the three-phase contact of solid-liquid and gas.
