  A number of dense particle suspensions experience a dramatic increase in
viscosity with the shear stress, up to a solid-like response. This
shear-thickening process is understood as a transition under flow of the nature
of the contacts, from lubricated to frictional, between initially repellent
particles. Most systems are now assumed to fit in with this scenario, which is
questionable. Using an in-house pressure sensor array, we provide a
spatio-temporal map of the normal stresses in the flows of two shear-thickening
fluids: a stabilised calcium carbonate suspension, known to fit in with the
standard scenario, and a cornstarch suspension, which spectacular thickening
behavior remains poorly understood. We evidence in cornstarch a unique, stable
heterogeneous structure, which moves in the velocity direction and does not
appear in calcium carbonate. Its nature changes from a stress wave to a rolling
solid jammed aggregate at high solid fraction and small gap width. The modeling
of these heterogenities points to an adhesive force between cornstarch
particles at high stress, also evidenced in microscopic measurements.
Cornstarch being also attractive at low stress, it stands out of the classical
shear-thickening frame, and might be part of a larger family of adhesive and
attractive shear-thickening fluids.
