Prevention of edge fracture using a nontoxic liquid metal sealant

Edge fracture, the sudden indentation of a viscoelastic fluid's free surface, often occurs when a sufficiently strong shear is applied to the fluid, rendering rheological measurements at high shear rates difficult. We show that sealing the fluid sample's free surface with the nontoxic liquid metal Galinstan can delay fracture occurrence, extending the measurable shear rate range of a cone-and-plate fixture by a decade. The method's effectiveness is compared to the cone-partitioned plate fixture, an existing tool for mitigating the adverse effects of sample fracture. Our cheap yet effective way to prevent edge fracture will benefit the general rheological study of complex fluids.