Slippery Surfaces Allow Sticky Pastes and Gels to Slide

Materials known as yield-stress fluids, including gels and pastes, can be found in consumer products such as food, condiments, and cosmetics, and in products in the energy and pharmaceuticals industries. Unlike other fluids such as water and oils, these materials will not start to flow on their own, even when their container is turned upside-down. Starting the flow requires an input of energy, such as squeezing the container.