The Fluid That Can Turn Solid In Milliseconds | ScienceBlobs

[00:00:00]Did you know that cornstarch and water mixtures can exhibit shear thickening, where viscosity can increase by over a hundredfold within milliseconds when impacted at speeds exceeding 1 m/s?

[00:00:13]This is caused by particle jamming in the suspension called discontinuous shear thickening.

[00:00:19]Even stranger, the critical stress threshold can be tuned by altering nanoparticle surface chemistry.

[00:00:26]This phenomenon defies classic Newtonian fluid dynamics and was first described in the 19th century, but still puzzles scientists today. One obscure fact is that under low stress, the particles in non-Newtonian fluids behave like lubricated spheres gliding past each other smoothly. But once the shear rate crosses a critical point, it triggers frictional contacts that lock particles forming transient solid-like structures similar to a traffic jam on a busy motorway. Another surprising detail is the role of hydroclusters, which are transient aggregates of particles formed under stress. These hydroclusters create localized regions of extremely high viscosity acting like microscopic shock absorbers, similar to how airbags deploy during a car crash to distribute force evenly. Finally, a rare insight is that some non-Newtonian fluids exhibit negative normal stress differences causing them to climb rotating rods or exhibit the Weissenberg effect.

[00:01:31]This counterintuitive behavior is due to polymer chain alignment generating elastic normal stresses comparable to tens of pascals, like tiny springs pushing fluid uphill against gravity. If you like this video, leave a like, comment, and follow for more videos from Science Blobs.