Dancing liquid crystals
Liquid crystal droplets in soapy water produce dazzling patterns.
These entrancing patterns are created by soapy molecules attracted to the surface of liquid crystal droplets in water.
Liquid crystals, fluids with aligned phases of constituent molecules, are used in everything from computer and television displays to mood rings. Since liquid crystals are made of rod-like molecules, they have special optical properties, such as changing color as they interact with electrical signals or light.
Surfactants like soap are attracted to the oil-like liquid crystals, changing the arrangement of the liquid crystal molecules and creating the striking patterns. Adding more soap to the solution changed the patterns (see animation below), while adding water reversed the changes.
Researcher Lisa Tran, a graduate student at the University of Pennsylvania in the US, also noted that – while the detailed patterns can only be seen under a microscope – changing the concentration of soap produced changes in the solution that were visible to the naked eye. This means the technique has potential for use in testing liquids for poisons or other contaminants.