The role of elastic instability on the self-assembly of particle chains in simple shear flow

Abstract

Flow-induced self-assembly (FISA) is the phenomena of particle chaining in viscoelastic fluids while experiencing shear flow. FISA has a large number of applications across many fields including materials science, food processing, and biomedical engineering. Nonetheless, this phenomena is currently not fully understood and little has been done in literature so far to investigate the possible effects of the shear-induced elastic instability. In this work, a bespoke cone and plate shear cell is used to provide new insights on the FISA dynamics. In particular, we have fine-tuned the applied shear rates to investigate the chaining phenomenon of micrometer-sized spherical particles suspended into a viscoelastic fluid characterized by a distinct onset of elastic instability. This has allowed us to reveal three phenomena never reported in literature before, i.e.,: (I) the onset of the elastic instability is strongly correlated with an enhancement of FISA; (II) particle chains break apart when a constant shear is applied for “sufficiently” long-time (i.e., much longer than the fluids' longest relaxation time). This latter point correlates well with the outcomes of parallel superposition shear measurements, which (III) reveal a fading of the elastic component of the suspending fluid during continuous shear flows.