Fabrication and optical properties of self-assembled films with micro needlelike arrays under magnetic field

The films with micro needlelike arrays, made of cobalt powders and fluorocarbon (FC) resin, were fabricated by self-assembly under the magnetic field. It is convenient to make micro arrays, and structures retain when external field is removed. The self-assembled films, treated under different field strength, were characterized by the stereoscopic microscope and scanning electron microscopy in detail. The density and shape of arrays varied as strengths of magnetic field increased. When the magnetic field reached to maximum, the space between two "needles" was 200-300 μm, the diameter of the middle of "needles" was about 20 μm, and the height of the arrays was 1-1.2 mm. The reflectance of the films with the needlelike arrays was lower than that of the films without magnetic field applied in the range of 300-2500 nm.