Magneto Twister: Magneto Deformation of the Water–Air Interface by a Superhydrophobic Magnetic Nanoparticle Layer

Remote manipulation of superhydrophobic surfaces provides fascinating features in water interface-related applications. A superhydrophobic magnetic nanoparticle colloid layer is able to float on the water-air interface and form a stable water-solid-air interface due to its inherent water repulsion, buoyancy, and lateral capillarity properties. Moreover, it easily bends downward under an externally applied gradient magnetic field. Thanks to that, the layer creates a stable twister-like structure with a flipped conical shape, under controlled water levels, behaving as a soft and elastic material that proportionally deforms with the applied magnetic field and then goes back to its initial state in the absence of an external force. When the tip of the twister structure touches the bottom of the water container, it provides a stable magneto movable system, which has many applications in the microfluidic field. We introduce, as a proof-of-principle, three possible implementations of this structure in real scenarios, the cargo and transport of water droplets in aqueous media, the generation of magneto controllable plugs in open surface channels, and the removal of floating microplastics from the air-water interface.