Credit: Image courtesy of reprinted with permission from Weston et al., Langmuir. © 2014 American Chemical Society.
A metal oxide nanoparticle gel (a) resisted flow and behaved as a “pseudosolid” under gravitational forces for five hours (b), but collapsed (c) when agitated with a force greater than the yield stress of the gel, which is the force necessary to make the gel flow. This breakdown of the structure is called “shear-thinning.”