Iranian Researchers Could Measure Contact Angle of Asymmetric and Symmetric Drops

Monday, September 10, 2018 - 13:25

Researchers from University of Tehran have developed a device for measuring contact angle of asymmetric and symmetric drops.

Farshid Chini, PhD, is Assistant Professor of Mechanical Engineering at the University of Tehran, and his colleague could develop the third generation of measurement device that can measure the surface tension and the contact angle of liquid droplets.

Contact angle is defined geometrically as the angle formed by a liquid at the three-phase boundary where a liquid, gas and solid intersect.

The low contact angle values indicate that the liquid spreads on the surface while high contact angle values show poor spreading. If the contact angle is less than 90° it is said that the liquid wets the surface, zero contact angle representing complete wetting. If contact angle is greater than 90°, the surface is said to be non-wetting with that liquid.

Contact angles can be divided into static and dynamic angles. Static contact angles are measured when droplet is standing on the surface and the three-phase boundary is not moving. Static contact angles are utilized in quality control and in research and product development. Contact angle measurements are used in fields ranging from printing to oil recovery and coatings to implants.

Based on his research, depending on the surface texture and external force orientations, a drop on a surface may be symmetric or asymmetric. This device can be applied for measuring contact angle of liquid droplets on the solid surface.

According to his previous research, the state-of-the-art contact angle measurement methods applicable to axisymmetric (symmetric) drops need a few of liquid parameters. Methods applicable to asymmetric drops (e.g. drops on inclined surfaces) may not be very accurate, and suitable for automated computer implementation. A new image processing based method, i.e. sub-pixel polynomial fitting (SPPF), to measure the contact angle of symmetric and asymmetric drops was presented.

As he explained, when a drop poured on a surface, it gradually becomes larger and away from the camera's focal length, so through this especial camera lens, the drop can be observed and analyzed in focal length.

Chini noted that the device can be applied in various industries including oil, gas, turbomachinery, weaving, pharmaceutical industries and etc.


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