Researchers at North Carolina State University have demonstrated that Janus particles - microscopic "two-faced" spheres whose halves are physically or chemically different - will move like little submarines when an alternating electrical field is applied to the liquid surrounding them. The micrometer-sized particles convert the electrical field into liquid motion around them and then propel themselves perpendicular to the direction of the powered electrodes instead of in the direction of the electrical field.
The phenomenon, known as "induced-charge electrophoresis," had previously been predicted through a theoretical model, but had never been demonstrated. The two-faced particles created by the research team were made of gold and plastic, and the electrical field was of similar voltage and frequency to those created by plugging an electrical device into a wall socket. Once stimulated by the electrical field, the particles always travel in the same orientation with the plastic face acting as the front of the submarine and the metallic face acting as the rear.
The name "Janus particle" comes from the name of a Roman god with two faces. Researchers believe the materials have the potential to perform a variety of applications. The next step, they say, is to create more complex particles capable of performing more specialized functions.
