Vortex flows impart chirality-specific lift forces

Chirality 101: Nature’s Left-Right Divide

Chirality describes objects that cannot be superimposed on their mirror image, like hands. In fluids, chiral particles (e.g., helical bacteria or engineered microstructures) interact uniquely with swirling flows. Unlike symmetric objects, their handedness dictates whether they drift inward or outward in a vortex .

Vortex Flows: More Than Just Whirlpools

In a Taylor-Couette cell (a fluid sandwiched between rotating cylinders), researchers observed that millimeter-sized chiral particles settle into stable orbits dependent on their handedness (Fig. 1). For example:

• Right-handed (R) particles spiral toward the vortex center.
• Left-handed (S) particles migrate outward .

This behavior arises from a lift force parallel to the shear plane, contrasting earlier models where forces acted perpendicularly .

Key Experiments and Hydrodynamic Insights

The 2015 Breakthrough

Hermans et al. demonstrated chirality-specific motion using a Couette cell with controlled rotation (Fig. 2a). Key findings:

Orbit Stability: Particles reached equilibrium orbits within ~30 minutes, with radii determined by chirality, not initial position .

Achiral Neutrality: Symmetric particles (disks/ellipsoids) showed no handedness-dependent drift .

Mathematical Model: A hydrodynamic framework explained how shear-induced rotation and orbital translation combine to create lift:
$$ vc approx kappa cdot frac{A L}{T ro} $$
Here, $ kappa $ is a chiral factor (+ve for R, -ve for S) .

Table 1: Chirality-Dependent Orbital Radii (Couette Cell Experiment)

Data adapted from

Beyond Fluids: Vortex Chirality in Materials Science

Ferroelectric Memory

In BiFeO₃ thin films, electric fields can switch the chirality of ferroelectric vortices. This offers a pathway for low-energy, high-density data storage (Fig. 3a) .

Magnetic Vortex Control

• Spintronics: Magnetic vortices in nanodisks can store data bits via polarity (up/down) and chirality (clockwise/counterclockwise). Current pulses or asymmetric geometries enable precise control .
• Non-Destructive Switching: Terahertz pulses flip vortex chirality without disrupting polarity, enabling multi-state memory .

Table 2: Methods of Chirality Control

Sources:

Future Frontiers: From Labs to Real-World Tech

Pharmaceutical Separation

Vortex-based microfluidics could replace costly chromatography for purifying enantiomers, slashing drug development costs .

Nanoscale Assembly

Chiral nanoparticles, guided by flow fields, could self-assemble into metamaterials with tailored optical or mechanical properties .

Quantum Materials

Chiral superconductors and topological insulators may leverage vortex dynamics for fault-tolerant quantum computing .

Conclusion: The Twisting Path Ahead

Vortex flows exemplify how fundamental physics can solve real-world problems. By harnessing chirality-specific forces, scientists are pioneering technologies that could redefine medicine, computing, and nanotechnology. As research progresses, the whirlpool’s secrets may soon swirl into our daily lives.

Tables and Figures

• Fig. 1: Couette cell experiment showing chiral particle orbits .
• Fig. 2: Hydrodynamic model of chiral drift .
• Fig. 3: Ferroelectric vortex switching under electric fields .

References
Embedded as throughout, citing key studies from the evidence list.