Needleless electrospray of magnetic film from magnetization-induced cone array

Electrospray is a simple and versatile approach to deposit thin-films. Traditionally, electrospray is achieved through capillary nozzle electrode to create fluid jet. Here, we report a novel needleless electrospray approach to continuously deposit the magnetic film from the magnetization-induced self-assembling cone array of poly(vinyl pyrrolidone) (PVP)/Fe3O4 ferrofluid without any nozzle and feed unit. A spiral tower is used to pump the PVP/Fe3O4 ferrofluid and a 3D peak-cluster is self-assembled on the tip surface under an external magnetic field. The multiple and parallel jets can be continuously emitted from the cone array of 3D peak-cluster, and get deposited on the aluminum foil as a smooth magnetic film when a high-voltage electric field is further applied. This needleless electrospray approach is simple, and cost-effective with a high productivity. The prepared magnetic film mainly composed of Fe3O4 nanoparticles and PVP polymer exhibits superparamagnetic property and good magnetic field responsive property.