Solidification of a cornstarch and water suspension

We report on an investigation of the solidification of a cornstarch and water suspension during normal impact on its surface. We find that a finite time after impact, the suspension displays characteristics reminiscent of a solid, including localized stress transmission, the development of a yield stress, and some elastic energy storage. The time dependence of these characteristics depends on the thickness of the cornstarch layer, showing that the solidification is a dynamic process driven by the impacting object. These findings confirm previous speculations that rapidly applied normal stress transforms the normally fluid-like suspension into a temporarily jammed solid and draw a clear distinction between the effects of normal stress and shear stress in dense suspensions.