This document discusses contact angle measurement and how surface roughness affects contact angle. It describes how contact angle is measured and depends on factors like temperature, humidity, and surface roughness. The document outlines an experiment where different surfaces were tested to find the relationship between surface roughness and contact angle. The results found that rougher surfaces like iron sheets and aluminum foil had higher contact angles, making them more hydrophobic, while smoother surfaces like glass slides and plant leaves had lower contact angles and were more hydrophilic. The experiment suggests hydrophobic surfaces have smaller distances between surface peaks, preventing water droplets from sitting on the surface.

1. Contact Angle Measurement
How does surface roughness affect
the contact angle?
M D Mali

2.  Contact Angle: The angle at which liquid/vapor interface meets solid surface,
measure of the ability of a liquid on a surface.
 Whenever the adhesive forces are stronger than the cohesive forces between the
surfaces, the contact angle is acute. The reverse case gives obtuse contact angles.
 Contact angle depends on factors like temperature, humidity, solid surface
roughness and static electricity etc.
 Physical properties of interaction between solids and liquid like wettability, affinity,
adhesiveness and repellency can be studied.
 Being an aquatic plant and living in muddy
habitats Lotus plants stay dirt-free without
using detergent and expending energy.

3. Designing And Procedure
 To find a surface-dependence of contact angle, we used
different surfaces of objects such as Iron sheet, aluminium
foil, marble tile, sprite can, TLC and leaves of different plants.
 Used PDMS to get the patterns of surface ; we transfer red
patterns used technique of “Lithographic patterning of two
dimensional structures”. By doing so, we avoided material
dependence of contact angle.
 Measured the contact angle of water droplet with the PDMS
patterned surface. Water droplets of around 5μL were used.
Images of the different patterns were taken using Goniometer.
 Images of the surfaces were also taken at 10X resolution using
microscope.

4. Results obtained
Object Contact Angle
Iron Sheet 103.218 Hydrophobic
Aluminium Foil 99.930 Hydrophobic
TLC 81.174 Hydrophilic
Marble Tile 90.029 -
Sprite Can 81.516 Hydrophilic
Leaf 1 65.692 Hydrophilic
Leaf 2 85.052 Hydrophilic
Glass Slide 65.824 hydrophilic

5. An attempt to establish a relation between surface roughness and contact angle is a very
tricky one. But here we are!
In general, the hydrophobic
surface has a more rough
surface in the sense that the
distance between two
consecutive peaks are small.
We suspect that this is smaller
than the size of the water
droplet, which is hence unable
to sit on the surface.
The hydrophilic substances have larger interstitial spaces where the water droplets
can fit comfortably.
Glass slide TLC (Aluminium) Leaf Sprite Can

6. PDMS, in its most general form, is hydrophobic. The observed surface trends
might change if we use a more hydrophilic substance in our experiment.
Future Application
•Water-proof paints
•Better understanding of wettability can help improve efficiency of fuel cells
•Construction of sticky surfaces
•Design hydrophobic substances to improve food-packaging
•Determine cleanliness of solid surfaces

7. REFERENCES
•Wikipedia
•Asknature.org
•Kandlikar and Steinke
•Vinaykumar Konduru
Thankyou