It all comes down to roughness
May 2, 2018 by PeÂter Rüegg, ETH Zurich
Lucio Isa and his team of researchers have explained how the surface characteristics of microspheres affect rapid increases in the viscosity of suspensions, thus laying the groundwork for applications such as smoothly flowing cement.
The internet is full of videos of people having fun running over white slime. It almost looks as if they were walking on water. But when they stand still, they slowly begin to sink. The slime in question is usually a concentrated suspension comprising cornstarch and water. Although colloquially known as "oobleck" after the children's book by Dr. Seuss, materials scientists use the term "non-Newtonian fluid". In contrast to a "normal" (Newtonian) fluid, non-Newtonian fluids can become more viscous when acted upon by a large, rapidly changing force. For a brief moment, the material behaves like a solid. However, if the force is constant and weak, the material flows like a normal liquid.
Read more at:
https://phys.org/news/2018-05-roughness.html#jCp
