IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 12, NO. 2, MARCH/APRIL 2007 283 Modeling and Characterization of Soft Magnetic Film Actuated 2-D Scanners Serhan O. Isikman, Student Member, IEEE, Olgac ¸ Ergeneman, Student Member, IEEE, Arda D. Yalcinkaya, Member, IEEE, and Hakan Urey, Member, IEEE Abstract—Magnetic behavior of polymer-based scanners is stud- ied in detail with emphasis on a new magnetic actuator model and dc deflection experiments. A 30-μm-thick permalloy sheet is plated on a polymer cantilever scanner and actuated using an external coil. Mechanical and magnetic modeling of the device and exper- imental results are presented. Shape anisotropy of the thin, soft magnetic film is explored for push and pull operation in different configurations. A new magnetic actuator model is developed based on the distributed point-by-point calculation of the magnetostatic moments and forces across the film surface. This effort helps one to obtain generic equations for magnetic force and torque without limiting the use of the model to the case where magnetic material is assumed to be fully saturated. Two-dimensional (2-D) scanning utilizing the orthogonal modes of the scanner, using only one actu- ation coil is presented. Index Terms—Magnetic actuators, magnetic torque, optical scanning, permalloy, scanner. I. INTRODUCTION M AGNETIC actuators have been used in different areas such as optical communications, display and imaging applications [1]–[7], biomedical applications, microfluidics [8], and relay switching [9]. Using magnetic actuators, relatively large forces can be obtained over large distances. They can make use of the Lorentz force [10], [11], [17], magnetostatic force with moving permanent magnets, or magnetic anisotropy torque with high-permeability thin films [4], [7], [11], [12], [16]. As illustrated in Fig. 1, the system described in this paper consists of a mirror suspended by a polymer cantilever beam, a permalloy sheet plated on the mirror, and an external coil to generate the driving magnetic field for dc and ac actuation. For the type of actuators studied in this paper, the simple linear magnetic circuit model studied in [15] fails, as most of the flux path is through the air. Furthermore, the saturated constant flux assumption cannot be used either [4], [5]. For a more accurate model, distributed magnetic moments and forces need to be computed using a nonlinear BH model for the magnetic film. Manuscript received August 9, 2006; revised January 29, 2007. This work was supported in part by Koc ¸ University-Migros Joint Program (KUMPEM) and in part by two Scientific and Technological Research Council of Turkey (T ¨ UB ˙ ITAK) under Project M ˙ ISAG-280-2004 and Project 104M161. S. O. Isikman and H. Urey are with Koc ¸ University, Istanbul TR-34450, Turkey (e-mail: hurey@ku.edu.tr). O. Ergeneman was with Koc ¸ University, Istanbul TR-34450, Turkey. He is now with Institute of Robotics and Intelligent Systems, ETH, Zurich, CH-8092, Switzerland. A. D. Yalcinkaya was with Koc ¸ University, Istanbul TR-34450, Turkey. He is now with the Departmnet of Electrical and Electronics Engineering, Bogazici University, Istanbul TR-34342, Turkey. Digital Object Identifier 10.1109/JSTQE.2007.893081 Fig. 1. Schematic (top) and photo (lower right) of the electrocoil-actuated scanner. The system consists of a narrow cantilever beam supporting a rectan- gular mirror and an electromagnet for actuation. Cross section between AA ′ line is shown indicating the materials used in the structure. Torsional rotation and out-of-plane bending mode motion directions are marked with arrows. Important contributions and novelties introduced by this study are: 1) demonstration of push or pull actuation by utilizing the shape anisotropy of the high-permeability magnetic films; 2) de- scription of a method for magnetic force and torque calculation valid in nonuniform magnetic fields and both in saturated and unsaturated magnetic materials; 3) experimental validation of the dynamic resonant actuation using composite polymer mate- rial as the structural layer and electrodeposited magnetic films; and 4) two-dimensional (2-D) scanning using a single external actuation coil suitable for certain imaging and display applica- tions. Millimeter-sized polymer devices are used in this study but the results are applicable to silicon microactuators as well. This paper is organized as follows. Section II gives the details of the device operation. Mechanical structure of the device, design issues, and applied magnetic actuation scheme are addressed. Section III describes the 2-D imaging application of the device where a single electrocoil is used for actuation in two axes. Section IV states conclusions and a summary of the future work. II. DEVICE OPERATION A. Structure of the Scanner A schematic diagram of the scanner system studied in this pa- per is shown in Fig. 1. The device consists of a narrow cantilever beam supporting a rectangular mirror and an electromagnet for actuation. Polymer is used as the structural material because of its simple fabrication steps and mechanical properties. Permal- loy is electroplated on the rectangular mirror part on one side and a 300-μm-thick silicon die with evaporated aluminum is 1077-260X/$25.00 © 2007 IEEE