The Hydrophobic Maze is a scientific toy that can be used to investigate what happens when you put water on super hydrophobic surfaces.

We used a laser cutter to cut two pieces of 3 mm MDF. One of them is the base and the other will define the walls of the maze.

To make the maze hydrophobic, we have to cover the whole surface with soot from a burning candle. CAUTION: before lighting the candle, be sure to remove any flammable materials from your work area. Carefully bring the maze to the top of the burning candle and direct the soot to the surface. It is very important to keep moving the maze, so the heat of the flame is not concentrated in only one spot. Cover the whole area with a thick layer of soot.

Place the maze on a level surface. Add some drops of water on the surface of the maze. Raise the corners of the maze and make the water drop move around. Try to get the drop to the other side of the maze.

The soot covers the wood surface turning it hydrophobic. Water is a very polar molecule, with strong interactions between its molecules. Soot is a non-polar material that makes a very rough and irregular surface. This makes the surface become super hydrophobic, and the water drops become round and move around freely.

You can ask your students to compare the behavior of water drops on the maze with other surfaces, like plastic, glass or wood. The strong intermolecular forces between water molecules are responsible for the high surface tension that makes the drops round.