Oobleck, a muddy mixture of cornstarch and water, is an example of what scientists term a discontinuous shear thickening fluid. Students marvel at its ability to support impulsive loads as if it were a solid. To investigate the counterintuitive substance, Deren Ozturk, Miles Morgan, and Bjørnar Sandnes of Swansea University in the UK shot pressurized air at oobleck sandwiched between two transparent plates 0.2 mm apart. These images show the substance’s response at various air pressures and cornstarch concentrations. Black regions are air pockets, and light regions are the cornstarch mixtures. The researchers were the first to use the thin oobleck sandwich to observe three distinct responses: viscous fingering, dendritic fracturing, and large-scale fracturing.
Viscous-fingering features are characterized by rounded edges. They can be seen in the first and third images in the top row, the second image in the middle row, and the third image in the bottom row....
