How to make square-shaped droplets
The shape of a liquid droplet can be controlled precisely by sandwiching it between two taut, elastic films. By varying the tension in the films, Rafael Schulman and Kari Dalnoki-Veress at McMaster University could create flat, elliptical, and almost square-shaped droplets. The experiment offers a relatively easy way to measure interfacial tension between liquids and elastic polymers and could also be used to create tuneable liquid lenses.
When a spherical liquid droplet comes into contact with a solid surface, the contact angle between the two substances can vary depending on a variety of properties, including the surface tension. The physics of this wetting process has been studied for over a century, but Schulman and Dalnoki-Veress realized that no-one had studied liquid droplets placed between two stretchable films.