MIT.nano October Seminar—Magnetics in MEMS: From DC to GHz

SPEAKER: Mark Allen, Alfred Fitler Moore Professor and Department Chair Electrical and Systems Engineering, University of Pennsylvania

ABSTRACT
The use of magnetic materials in microelectromechanical systems (MEMS) - both magnetically soft (permeable materials) and magnetically hard (permanent magnets) - opens rich new applications sets for MEMS. This presentation will discuss multiple applications based on magnetic MEMS: point-of-load power conversion, adaptive RF filtering of microwave signals, and magneto-optomechanical relays for EMI-immune switch control.

To achieve compact switching power converters, both switching at high frequency and the use of high saturation flux density materials such as iron-based alloys are desirable. However, at high switching frequencies, electrically conducting magnetic materials may suffer from eddy current loss. Allen will discuss a materials fabrication technique that allows additive fabrication of a multiscale magnetic material from a large number of insulated iron alloy sheets (lamina), at individual sheet thickness scales that suppress eddy currents (on the order of submicron to microns), and at total thicknesses (on the order of tens to hundreds of microns) that allow significant power handling. Applications in step-down power conversion for electronic systems and universal input (100-220V) chargers, as well as step-up conversion for compact powering of piezoelectric actuators, will be discussed.

In the adaptive filter application, the use of magnetics in yttrium iron garnet (YIG) spin-wave filters will be presented. YIG has an interesting property that the allowed propagation frequency of spin waves through this material depends on the magnitude of an externally applied static magnetic field. By varying this external magnetic field, the filter frequency can be changed without any geometric adjustment to the YIG itself. Current commercial approaches to YIG-based adaptive filters involve the use of power-intensive electromagnets; Allen will discuss the use of programmable permanent magnetic circuits to create adaptive filters in the GHz range that consume zero DC power.

Finally, in high power conversion applications, optical control of the gate drives of switching converters prevents transient noise from interfering with shutoff signals in the event of a fault. Allen will discuss an integrated photonic circuit with a surface micromachined magnetic suspension that can interfere with the evanescent wave of an optical signal propagating through an integrated waveguide, attenuating the signal and turning off the switching transistors in the event of an overcurrent fault.

Visit the event webpage: https://mitnano.mit.edu/events/oct-seminar-allen