Presently micro inductors are fabricated as spirals

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Unformatted text preview: ransformers, and magnetic actuators. Presently, micro-inductors are fabricated as ‘spirals’ or ‘square spirals’ in 2-D layouts, as shown below: [Fig. 8.9 from ‘Foundations of MEMS’, Chang Liu] © N. Dechev, University of Victoria 7 2D Spiral Micro-inductors 2-D micro-inductors, such as the one shown in Fig. 8.9(a) are simple to fabricate. However, they are not too effective due to their spiral shape, and the relatively low magnetic permeability of air or free space. To improve their performance in creating a strong magnetic field, the magnetic cores have been fabricated at their center, as shown below: [Fig. 8.9 from ‘Foundations of MEMS’, Chang Liu] However, the resulting improvements are marginal. © N. Dechev, University of Victoria 8 2D Spiral Micro-inductors An even bigger problem with ‘in-plane’ micro-inductors is their poor efficiency, or ‘quality factor’ since they are fabricated inplane with the substrate. By being in-plane with the substrate, the magnetic flux must pass through the silicon substrate, which is conductive, yet has a high resistance. Eddy currents will form in the substrate, and degrade the performance of the device. © N. Dechev, University of Victoria 9 3D Micro-inductors In order to avoid the problems with 2D in-plane micro-inductors, researchers are attempting to construct 3D micro-inductors with magnetic cores, and without cores. The primary motivation is to minimize the amount of magnetic flux that must pass through the substrate. © N. Dechev, University of Victoria [Fig. 8.11 from ‘Foundations of MEMS’, Chang Liu] 10 Monolithic Fabrication of 3D Micro-inductors The micro-inductors shown below are fabricated using surface micromachining, or similar thin-film fabrication technologies. Micromachined, 3D micro-inductors [Microfabrica.com] HARM fabricated, 3D micro-inductors [KAIST] © N. Dechev, University of Victoria 11 Case Study 8.2: Self-Assembly of 3D Micro-inductors CASE 8.2. Magnetic Beam Actuation: (Self Assembly of Magnetic Beams) Here, a powerful electromagnet is used to create an...
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