Acoustically Induced Superthickening and Enhanced Elasticity in Shear Jamming Dense Colloidal Suspensions

Acoustic perturbation can dramatically enhance the solid properties of a shear jammed suspension.

The application of a transient acoustic perturbation (training) prior to shear jamming was shown to result in the suspension remaining shear jammed when later exposed to a perturbation (testing) that would have otherwise resulted in unjamming. The state of the suspension prior to testing was studied via rate cessation and small amplitude oscillatory shear (SAOS). It was found that the stress relaxation timescale increases with the power applied during training. Strikingly, beyond a critical training power, the stress increases instead of decaying during cessation. SAOS experiments show that the storage modulus immediately before testing increases with training power. As SAOS is applied, the storage modulus decays and reaches a stable value which can be orders of magnitude larger for large training powers when compared to an untrained suspension.

Training was also found to significantly reduce the time taken for shear jamming to occur, promoting what would have been a discontinuously shear thickening phase to a shear jamming phase. These results demonstrate the tremendous potential acoustic perturbation has for controlling the flow and elasticity of dense colloidal suspensions.