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

• Published in: IEEE transactions on magnetics Vol. 58; no. 2; pp. 1 - 5
• Main Authors: Fontana, Erika, Motyckova, Lucie, Tomba, Caterina, Keller, Frederico Orlandini, Groza, Georgiana, Bonfim, Marlio, Ranno, Laurent, Devillers, Thibaut, Dempsey, Nora M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE); Institute of Electrical and Electronics Engineers
• Subjects: Anisotropic bonded magnet; Arrays; Condensed Matter; Electromagnetism; Electromagnets; Engineering Sciences; Ferrites; flexible polymer-bonded magnet; Hall probes; hard magnetic material; Magnetic field measurement; Magnetic hysteresis; Magnetic resonance imaging; Magnetism; Magnetization; Magnetometers; Materials Science; Permanent magnets; Perpendicular magnetic anisotropy; Physics; Polydimethylsiloxane; Powders; Reactive ion etching; SmFeN; Tapering; Thickness; Three axis; SmFeN; hard magnetic material; anisotropic bonded magnet; flexible polymer-bonded magnet
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2021.3088048

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 <inline-formula> <tex-math notation="LaTeX">300~\mu \text{m} </tex-math></inline-formula> and their in-plane dimensions from 20 to <inline-formula> <tex-math notation="LaTeX">400~\mu \text{m} </tex-math></inline-formula>. Powder alignment was achieved using a bulk NdFeB magnet. Arrays of micro-pillars of height <inline-formula> <tex-math notation="LaTeX">300~\mu \text{m} </tex-math></inline-formula> and width tapering from <inline-formula> <tex-math notation="LaTeX">300~\mu \text{m} </tex-math></inline-formula> at their base to <inline-formula> <tex-math notation="LaTeX">200~\mu \text{m} </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">13~\mu \text{m} </tex-math></inline-formula> at the maximum applied field value of 100 mT.