Fabrication and Characterization of Polymer-Bonded Flexible Anisotropic Micro-Magnet Arrays

Here, we present a process for the fabrication of arrays of anisotropic flexible bonded micro-magnets attached to a transparent base. The micro-magnets are based on hard magnetic SmFeN or Sr-ferrite powders mixed with polydimethylsiloxane (PDMS). The size, shape, and distribution of the micro-magnets are defined using a Si-mold fabricated by deep reactive ion etching (DRIE). The volume fraction of the magnetic powder was fixed at 30% while the thickness of the micro-magnets ranged from 50 to 300~\mu \text{m} and their in-plane dimensions from 20 to 400~\mu \text{m} . Powder alignment was achieved using a bulk NdFeB magnet. Arrays of micro-pillars of height 300~\mu \text{m} and width tapering from 300~\mu \text{m} at their base to 200~\mu \text{m} at their top were characterized using a vibrating sample magnetometer (VSM) and a scanning Hall probe microscope (SHPM) and the results of the latter were compared with analytical simulations. The homogeneous magnetic field produced by a three-axis electromagnet was used to move the micro-pillars in a controlled fashion. The field induced in-plane displacement of the SmFeN-based pillars was more than three times greater than that of the Sr-ferrite-based ones, reaching 13~\mu \text{m} at the maximum applied field value of 100 mT.