Electromagnetically driven, environmentally adaptive, and functionally switchable hydrodynamic devices

TL;DR

The paper addresses non-intrusive, multifunction hydrodynamic control by introducing a meta-hydrodynamics framework that uses externally applied force fields to mimic changes in fluid properties. It derives volumetric force distributions $\boldsymbol{F}_1$ and $\boldsymbol{F}_2$ from a viscous–potential-flow equivalence and homogenizes $\boldsymbol{F}_2$ to a single-direction force $\bar{\boldsymbol{F}}_2$, with the key relation $\bar{F}_{2x} = \dfrac{R_1^2}{R_1^2 - R_2^2} F_{1x}$. Electromagnetic forces in a conducting fluid, arranged via applied voltages and magnetic fields, realize these distributions to achieve cloaking, shielding, and amplification. Numerical simulations and experiments validate the approach, showing dynamic switching among functions with robustness across fluids and environments, and suggesting broad applicability in microfluidics and related fields.

Abstract

Metamaterials provide exceptional control over physical phenomena, enabling many disruptive technologies. However, researches in hydrodynamic meta-devices have mainly used intrusive methods to manipulate material structures, limited by material properties and specific environmental conditions. Each design serves a single function, reducing versatility. This study introduces a meta-hydrodynamics theory using applied force fields to avoid physical contact with the fluid and eliminate the need for inhomogeneous and anisotropic metamaterials, allowing continuous switching between cloaking, shielding, and Venturi amplification. The force field operates independently of the fluid's physical properties, making it adaptable to various fluids and environmental conditions. We derive volumetric force distributions for hydrodynamic devices based on fluid properties and forces equivalence, using the integral median theorem to homogenize these forces for practical applications. The effectiveness of the proposed hydrodynamic devices is validated through numerical simulations and quantitative analyses. By utilizing the electromagnetic forces produced by the interaction between a conducting fluid and an electromagnetic field, we experimentally verified the validity of our theoretical simulations. Our research offers different insights into hydrodynamic meta-devices design, enhancing practical applications and opening avenues for innovative flow manipulation.

Figures (3)

• Figure 1: Schematics of the hydrodynamic devices. (A) Schematic of the hydrodynamic devices with Venturi amplification, shielding and cloaking functions. The amplification (shielding) function promotes (prevents) fluid from entering the central region without disturbing the background flow field; the cloaking function removes interference with the flow field caused by obstacle in the center. The $x-y$ plane for the shielding function of the hydrodynamic devices, and the magnetic field in the opposite direction enables the amplification function. The hydrodynamic devices have inner and outer radii denoted as $R_1$ and $R_2$, respectively. In regions 1 and 2, the magnetic induction intensities are $B_1$ and $B_2$, respectively. (B) Schematic of the experimental setup for the cloaking function of the hydrodynamic devices, where the flow channel has the same three-dimensional dimensions as the model in (A). (C) The ability of hydrodynamic devices to function independently of the background environment suggests potential applications in areas such as drug delivery, nanomedicine, chemical reaction, and Venturi tube.
• Figure 2: Numerical simulation and experimental validation results. (A) Relationship between the manipulation effects of hydrodynamic devices and the hypothesized viscosity across various regions. (B) Linear relationship between ${\bar{F}}_{2x}$ and $F_{1x}$. (C) Volumetric forces $\boldsymbol{F}_2$ for cloaking, shielding, and amplification, where the negative sign indicates the opposite direction to the positive direction of the coordinate axis. (D) Characterization of the temporal dynamics of volumetric forces. (E) Velocity fields (localized) for the cases of the bare, obstacle, cloaking, shielding, and Venturi amplification, where the black lines represent streamlines and the white lines denote isobars. (F) Experimentally observed streamlines (black), where the fluid flows from the left to the right side of the photos. The white dotted line delineates the range of the hydrodynamic devices.
• Figure 3: Multiphysics simulation results, as well as comparisons of velocity distributions for hydrodynamic cloaks, shields, and amplifiers. (A, B) Multiphysics coupling results (plane of $z=0$, localized), where the black lines represent streamlines, the white lines indicate the equipotential lines, and the red arrows denote the direction of the magnetic field. (A) Cloaking ($\boldsymbol{F}^\prime$ and $\bar{\boldsymbol{F}}$), shielding ($\bar{\boldsymbol{F}}$), and amplification ($\bar{\boldsymbol{F}}$) under electromagnetic forces. (B) Potential distributions around an insulating obstacle and within pure fluids.(C) Velocity distributions along the characteristic line $x=0$ for different cases.