Thamires Lima, a research professor in chemical engineering at Drexel University, studies the properties of thick, viscous liquids — think honey or molasses, though in a lab you’re more likely to find polypropylene or crude oil. Using a method called extensional rheology, Lima stretches liquids between metal plates to find the force that makes them flow. A few years ago, she was conducting a test as part of a project in collaboration with the oil and gas company Exxon Mobil when she heard a shor...