Unidirectional zero-index and omnidirectional hybrid hydrodynamic cloaks constructed from isotropic media with anisotropic geometry

TL;DR

This paper introduces a novel hydrodynamic cloaking method using isotropic media with anisotropic shapes, achieving improved flow manipulation and reduced disturbances compared to traditional cloaks, validated by simulations and experiments.

Contribution

The authors develop a zero-index hydrodynamic cloak based on pseudo-conformal mappings and introduce a hybrid design that enhances omnidirectional flow control without viscosity tuning.

Findings

Zero-index cloaks significantly reduce flow disturbances.

Hybrid cloaks outperform conventional and zero-index designs.

Validated through simulations and experimental tests.

Abstract

Hydrodynamic cloaking offers a promising approach for manipulating viscous flows by redirecting fluid around an obstacle without inducing external disturbances. By extending pseudo-conformal mappings into potential flow models, we introduce a new isobaric boundary condition that enables the construction of zero-index cloaks using isotropic and homogeneous media shaped into anisotropic geometries, such as elliptical shells. Compared to conventional cloaks, which suffer performance degradation under realistic viscous conditions, the zero-index design significantly reduces such losses by suppressing flow disturbances at the inner boundary. To overcome practical limitations in realizing ideal isobaric conditions, we further propose a hybrid cloak that integrates a raised fluid domain with an auxiliary flow channel above the obstacle. This architecture removes the need for viscosity tuning and, under anisotropic geometries, surpasses both conventional and zero-index cloaks in omnidirectional performance. The design is validated through simulations and experiments. Our findings offer a generalizable strategy for controlling viscous flows and open new directions for microfluidic applications including drug delivery, particle steering, and cell sorting.