# Controlling Shear Jamming in Dense Suspensions via the Particle Aspect Ratio

## TL;DR

This study systematically investigates how particle shape anisotropy influences shear jamming in dense suspensions, revealing that increased aspect ratio lowers the packing fraction needed for jamming, independent of frictional interactions.

## Contribution

It is the first systematic study to isolate and analyze the effect of particle aspect ratio on shear jamming, separate from interparticle friction effects.

## Key findings

- Increasing aspect ratio reduces the minimum packing fraction for shear jamming.
- Shear thickening and jamming behaviors can be independently controlled through shape and friction.
- Suspensions with high aspect ratio particles exhibit shear jamming at packing fractions as low as 33%.

## Abstract

Dense suspension of particles in a liquid exhibit rich, non-Newtonian behaviors such as shear thickening and shear jamming. Shear thickening is known to be enhanced by increasing the particles' frictional interactions and also by making their shape more anisotropic. For shear jamming, however, only the role of interparticle friction has been investigated, while the effect of changing particle shape has so far not been studied systematically. To address this we here synthesize smooth silica particles and design the particle surface chemistry to generate strong frictional interactions such that dense, aqueous suspensions of spheres exhibit pronounced shear jamming. We then vary particle aspect ratio from $\Gamma$=1 (spheres) to $\Gamma$=11 (slender rods), and perform rheological measurements to determine the effect of particle anisotropy on the onset of shear jamming and its precursor, discontinuous shear thickening. Keeping the frictional interactions fixed, we find that increasing aspect ratio significantly reduces $\phi_m$, the minimum particle packing fraction at which shear jamming can be observed, to values as low $\phi_m=33\%$ for $\Gamma$=11. The ability to independently control particle interactions due to friction and shape anisotropy yields fundamental insights about the thickening and jamming capabilities of suspensions and provides a framework to rationally design shear jamming characteristics.