Experimental study of liquid droplet spreading on patterned surface

• Main Author: Seow, Mei Hui.
• Other Authors: Fan Hui
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/53579
• Institution: Nanyang Technological University

This report documents the research and experimental study on the liquid spreading on line patterned surfaces. The objectives of this experimental study are to find out how liquid droplet spread on matching concave and convex surfaces by measuring the contact angle. Through the contact angle, relationship between spreading of liquid droplet and the different surfaces can be determined. A suitable experimental setup for this experiment study is also designed to conduct the investigation. In this experimental study, a total of four concave and four convex line patterned surfaces are being studied, with line width of 20 µm, 40 µm, 80 µm and 20 µm and with spacing of 200 µm, 180 µm, 140 µm and 400 µm respectively. The height of the lines for the convex surfaces and the depth of the lines for the concave surfaces are 5 µm. Contact angles are measured from two directions for each surface, longitudinal direction which is parallel to the line pattern and lateral direction which is perpendicular to the line pattern, using a microscope. The contact angles are measured using software named Supereyes. An adjustable micro-pipette is used to form the droplets of 4 µl or 10 µl. Major findings from this study are, from the results, it can be seen that contact angles measured in the lateral direction are generally smaller than the contact angle measured in the longitudinal direction. Another trend is that for concave surfaces, when the volume of droplets increases, the contact angle measured decreases. However, for convex surfaces, when the volume of droplets increases, the contact angle measured increases. Lastly, the other trend is that the spacing length vs. vertical contact angle results in a quadratic curve for the concave surface while the spacing length vs. horizontal contact angle results in an exponential curve for the concave surface.