Magnetic Gradient Slippery Surfaces with Shape Memory Property for Smart Sliding Control of Superparamagnetic Droplet

A kind of magnetic material with gradient shape was prepared, which is composed of magnetic particles and shape memory polymers. After further coating the dimethyl silane lubricant, we obtained a magnetic gradient slippery surface. A superparamagnetic droplet can self -transport directionally on the surface under the effect of magnetic gradient. Meanwhile, reversible control of surface morphology can be achieved based on the shape memory effect, which is favorable for on/off control of droplet sliding. Based on the above two merits, the combination of directional self -transportation and on/off sliding control was successfully achieved. In addition, we also investigated the influence of magnetic particles content on the shape memory property of materials in detail and the relationship between the deformation size of surface morphology and superparamagnetic droplet sliding performance. The mechanism analysis further demonstrates that the self -transportation of superparamagnetic droplet is driven by the directional force provided by magnetic field gradient, the resistance can be increased/eliminated during droplet self -transportation by the reversible control of the morphology of the surface. The synergistic effect of these two factors endows the surface with excellent manipulation of superparamagnetic droplet.