Printing superparamagnetic colloidal particle arrays on patterned magnetic film

Thin ferromagnetic film patterned into isolated islands is used to direct the assembly of superparamagnetic colloidal particles into two-dimensional (2D) arrays. It is confirmed that only one particle per island is retained when particles are slightly larger than the island, whereas particles that are smaller can form various patterns on the islands. Ferromagnetic islands positioned under a template of microwells are shown to promote highly regular 2D arrays, and external uniform magnetic field can be used to bias the particles to attract or to repel from the exposed end of the ferromagnetic islands. (C) 2003 American Institute of Physics.