Reversible shear thickening at low shear rates of electrorheological fluids under electric fields

TL;DR

This study demonstrates reversible shear thickening in electrorheological fluids at low shear rates and high electric fields, revealing the role of electrostatic interactions and inter-particle friction in shear strength control.

Contribution

It introduces a new understanding of shear thickening behavior in ER fluids under electric fields, highlighting electric field control of shear thickening at low shear rates.

Findings

Reversible shear thickening occurs above 1 s-1 shear rate and 100 V/mm electric field.

Shear thickening is linked to electrostatic particle interactions and inter-particle friction.

Electric field modulates the extent of shear thickening, impacting ER fluid applications.

Abstract

Shear thickening is a phenomenon of significant viscosity increase of colloidal suspensions. While electrorheological (ER) fluids can be turned into a solid-like material by applying an electric field, their shear strength is widely represented by the attractive electrostatic interaction between ER particles. By shearing ER fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (<1 s-1) and a high critical electric field strength (>100 V/mm), which could be characterized by a modified Mason number. Shear thickening and electrostatic particle interaction-induced inter-particle friction forces is considered to be the real origin of the high shear strength of ER fluids, while the applied electric field controls the extent of shear thickening. The electric field-controlled reversible shear thickening has implications for high-performance ER/magnetorheological (MR) fluid design, clutch fluids with high friction forces triggered by applying local electric field, other field-responsive materials and intelligent systems.