Inertia-Dilatancy Interplay Governs Shear-Thickening Drop Impact

TL;DR

This study combines experiments and modeling to reveal three impact regimes of shear-thickening fluids, uncovering a counterintuitive liquid-like response at high shear rates and developing a unified impact model.

Contribution

It introduces a comprehensive model integrating impact theory and dilatancy mechanics to describe shear-thickening drop impacts across regimes.

Findings

Identification of three impact regimes including a novel liquid-like onset

Development of a unified quantitative impact model

Observation of counterintuitive high shear-rate liquid-like response

Abstract

Combining high-speed photography with direct force measurements, we investigate the impact dynamics of drops of cornstarch-water mixtures -- a premier example of shear-thickening fluids -- across a wide range of impact conditions. Our study identifies three distinct impact regimes. In addition to the liquid-like and solid-like behaviors generally expected for the impact-induced response of shear-thickening fluids, we uncover a counterintuitive regime in which high-concentration cornstarch-water mixtures display a liquid-like response at the onset of impact when shear rates are high and only transition to a solid-like behavior at later times as shear rates reduce. By integrating the classic drop-impact theory with the Reynolds-Darcy mechanism for dilatancy, we develop a unified model that quantitatively describes the impact dynamics of shear-thickening drops across all regimes. Our work reveals the unexpected response of shear-thickening fluids to ultra-fast deformation and advances fundamental understanding of drop impact for complex fluids.