Droplet shape calculator*
When a droplet equilibrates on a solid surface it takes a shape which was first described by Thomas Young and Pierre-Simon Laplace in 1806. Here we demonstrate an online droplet shape calculator software based on the above theoretical analysis.
In particular, the equilibrium droplet shape is obtained by solving the Young-Laplace equation(1),(2), which states the force balance between surface tension, Laplace pressure and gravity, along the free surface of the droplet. The wettability of the solid material is then introduced through the Young contact angle, i.e. the angle formed by the intersection of the liquid-solid and the liquid-ambient interfaces.
In order to compute the shape of a water droplet(3), the user should define the Young contact angle (between 20o, for a water droplet on a hydrophilic glass substrate, and 120o for a droplet on a hydrophobic Teflon® substrate) and the gravitational acceleration (between 9.8 m/s2, for a water droplet on Earth, and 24.8 m/s2 for the same droplet on Jupiter!). The volume of the droplet is 15 μl (= 15 × 10-9 m3).