Surface force apparatus

Do you remember playing with two magnets which either attract or repel each other? You might have felt a force between those two magnets. A surface force apparatus (SFA) is similarly built but instead of magnets, it studies the force between two solid surfaces.

The SFA looks like a big sandwich maker but instead of bread slices, it has two tiny pieces of material that scientists want to study. Usually, these materials are solids like metals or polymers. There is a tiny gap between the two materials, which is filled with a special liquid-like oil or water.

Scientists then press the two materials together using a tiny machine called a motor. They move the two materials very, very slowly and measure any forces between them using special sensors.

This technique helps scientists to understand how the surfaces stick together and what kind of forces and interactions are happening between them. It is especially helpful for scientists who want to develop new materials or study how things stick together in our bodies like proteins or cells.