Taiji Patterns Swirled Out of Magnetic Liquid Metal Fluids Under Rotating Magnets

ABSTRACT While magnetic fluids are well known for their rich ferrohydrodynamic behaviors, prior research on dynamic droplet morphologies has largely been confined to nonconducting materials. By contrast, electrically conductive magnetic liquid metals offer a broader space for exploration while also presenting intriguing unsolved mysteries. Here, we disclose a series of profound fluidic phenomena observed in magnetic liquid metal droplets, ranging from millimeter to centimeter scales, under the influence of a rotating magnet pair. The resulting flow patterns resemble the classical Chinese Taiji diagrams—a philosophical system describing genesis and transformation. By systematically varying droplet volume, magnetic field strength, and rotational speed, we achieved precise control over diverse morphologies, including ellipses, dumbbells, toroidal rings, and Yin‐Yang symbols, quantified their dependence on experimental parameters, and constructed three phase diagrams to characterize the corresponding regimes. The underlying mechanisms of droplet separation and coalescence were further interpreted from an energy perspective. These findings provide significant experimental insights and a theoretical framework for advancing fundamental magnetohydrodynamics and related engineering applications.