Transcript Slide 1

Magnetic MEMS and Micropower Systems
David P. Arnold
Assistant Professor
Interdisciplinary Microsystems Group
Department of Electrical and Computer Engineering
University of Florida
229 Benton Hall
PO Box 116200
Gainesville, FL 32611-6200
(352) 392-4931 phone
(352) 392-1104 fax
[email protected]
http://www.img.ufl.edu
Magnetic MEMS & Micropower Systems
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Overview
 Microscale Magnetics
 Advantages
 Challenges
 Applications
 Magnetic MEMS Applications
 Microactuators
 Vibrational Energy Harvesting
 Micromotors/Generators
 Magnetic Self-Assembly
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MEMS Overview
 Microelectromechanical Systems (MEMS) - integration of mechanical
elements, sensors, actuators, and/or electronics on a common silicon
substrate through microfabrication technologies
Ultrasonic Proximity
Transducer/Sensor
Capacitive Microphone
Electroosmotic Pump
Packaged Piezoresistive
Microphone
3-Axis Capacitive Accelerometer
1mm
Thermally Actuated Micromirror
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Microscale Magnetics
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MEMS Transduction Schemes
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Various energy-transduction mechanisms for MEMS
 Piezoelectric
 Thermal
 Electrostatic
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Electromagnetic (Electrodynamic and Magnetic)
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Relatively large forces over large displacements
High magnetic fields without material damage
Joule heating of conductors
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Magnetic forces are body forces (electrostatic are surface forces)
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Types of “Magnets”
Hard Magnet
(“magnet”, “permanent magnet”)
Ferromagnetic Materials
Electromagnet
Soft Magnet
(“back iron”)
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Electrodynamic Actuation
1. Electrodynamic: motor action produced by the current in an electric
conductor located in a fixed transverse magnetic field (e.g., voice coil).
i
2
F  Bli
S
N
1
F

Cone
Cone
Diaphragm
Coil
Frame
Flexible
Diaphragm
Magnet
Magnet
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Magnetic
Yoke
Coil
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Magnetic Transduction
2. Magnetic: motor action produced by the tendency for magnetic
moments to align and/or close a magnetic air gap (e.g., solenoid).
A. Electromagnet - Magnet
2
F
2 μ0 Ag
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Magnetic Actuation
B. Magnet - Magnet
-
No transduction (only magnetic energy domain)
Uses: Bistable “latches”, Bonding, Constant mechanical force

 
F   μ0( H  M )dV
V
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Magnetic Scaling Laws
MagnetMagnet
k = scale reduction; ki = current density increase
Electrodynamic
O. Cugat, J. Delamare, and G. Reyne, “Magnetic Micro-Actuators and Systems
(MAGMAS),” IEEE Trans. Magn., vol. 39, no. 5, Nov. 2003.
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ElectromagnetMagnet
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Microscale Magnetics
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Challenges for Microscale Magnetic Systems
Processe
s
1. Process Limitations
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PVD (Sputtering/Evaporation)
Electroplating
Spin-coating
Geometries
Materials
2. Material Limitations
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Material selection limited by deposition processes
No “advanced processing” capabilities (quenching, rolling,
sintering, annealing, etc.)
3. Geometries
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“Thick” magnetic films (10’s or 100’s of microns)
Three-dimensional solenoidal coils
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Coils
 Multilevel Electroplating
 Usually Cu or Au
NiFe-core inductor [J. Y. Park, 1998].
Planar spiral coil
Planar Cu windings
3D air core RF inductors [Y.-K. Yoon, 2003].
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Magnetic Thick-Films
 Electrodeposited Magnetic “Thick” Films
 10’s or 100’s of μm thick
 Soft Magnets: NiFe, NiFeMo, CoFe, etc.
 Hard Magnets: CoNiP, CoPt, FePt
Electroplated CoNiP, Guan & Nelson., 2005
60 μm
Electroplated CoPt magnets, Zana et al., 2004-5
Electroplated NiFe core and Cu windings in a
planar induction motor, Cros et al., 2004
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Magnetic Actuators
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Magnetic Valve
 Electromagnet-Magnet actuation
 Magnet-Magnet bistability
 Surface-micromachined (multi-level electroplating)
 Cu coil, NiFe superstructure, CoPt PM
Permanent
Magnet
Ferromagnet
Coil
J. Sutanto, Ph.D. Dissertation, Georgia Tech, 2004
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Electrodynamic Speaker
 Electrodynamic actuation using fringing fields
 Bulk-micromachined
 Silicon nitride membrane
 Electroplated copper coil
 NdFeB permanent magnet (bulk)
M.-C. Cheng, et al., “A Novel Micromachined Electromagnetic Loudspeaker for Hearing Aid,”
Proceedings of Eurosensors XV, Munich, Germany, Jun 10-14, 2001
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Electrodynamic Actuator
 Proposed Electrodynamic
Actuator
 Extend concept of
Cheng, et al., but use
multiple micromagnets
 “Swiss roll” spiral coil
design
Coil
Rigid Piston
Permanent
Micro
Magnets
Coil
 Applications:
 Microspeaker
 Flow-control actuator
(synthetic jet)
Substrate
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Microscale Power Systems
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Vibrational Energy Harvesters
 Electrodynamic and magnetic transducers for harvesting “waste” (μWmW scale) power from oscillating or vibrating systems
 Examples: self-powered sensors, hybrid power sources
dΦ
V N
dt
Vibrational Energy Harvesting Scheme
Permanent
Magnet
Energy
Storage
Vibrating Body
Coils
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Vibrational Magnetic Generators
 Theoretical Performance Estimates
P  mY02 ωn2
 Human Powered: μW/cm3 range (1-10 Hz)
 Vibrating Structure: mW/cm3 range (0.1-1 kHz)
P. D. Mitcheson, et al., “Architectures for Vibration-Driven Micropower
Generators”, Journal of MEMS, vol. 13, no. 3, June 2004.
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Vibrational Magnetic Generators
 Published articles
Output
Power
Resonant
Freq.
Vibration
Amplitude
Size
Power
Density
Yates, et al.,
1995-96
0.3 μW
4400 Hz
0.5 μm
4.4 mm3
70 μW /cm3
Anantha, 1998
400 μW
Li et al., 2000
40 μW
80 Hz
200 μm
1 cm3
40 μW /cm3
El-hami, 2001
530 μW
320 Hz
25 μm
240 mm3
2.2 mW/cm3
P. Glynne-Jones,
et al. 2004
157 μW
3.15 cm3
50 μW/cm3
Kulkarni, et al.,
2006 (*theoretical)
128 μW
43 mm3
3.0 mW/cm3
7.4 kHz
240 μm
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Microengine Concept
Turbine Engine
Electrical Generator
Hydrocarbon Fuel
- >3,000 W·hr/kg
(25 % efficiency)
- Compact (few cm3)
- Refuelable
12,000-14,000
W·hr/kg
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Integrated Microengine
 Integrated Gas-Turbine Engine and
Electrical Generator
 10 - 100 W
 High speed (~1 Mrpm)
 High temp. (300 - 1400˚C)
10 mm
[M. A. Schmidt, 2002]
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Silicon-Based Magnetic Induction Machine
 Integration of magnetics in silicon
 2.5 mN-m motoring torque
 33 mN-m/cm3 torque density
Tethered Rotor
Stator
Upper
Wafer
250 mm
10 mm
20 mm
Lower
Wafer
Fusion-Bonded
Stator (cutaway view)
Rotor
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High-Speed Permanent-Magnet Generator
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Hybrid microfabrication and assembly
300,000 rpm
8 W DC power delivered
>40 W/cm3 power density (10-20x
larger than macroscale)
Rotor
Stator
Magnet Poles
Rotor
Stator
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Magnetic Self-Assembly
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Assembly of Small Components
 Conventional Assembly of Small Components
 Device subcomponents fabricated
separately
 Assembled together in serial fashion
 Robotic pick and place
 Issues with Conventional Approach
 Manufacturing bottleneck
 Manipulation of small parts
 Alignment and positioning tolerances
 “Sticking” problem
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Self-Assembly
 Mixing Forces
 Fluidic flow
 Vibrational energy
 Bonding forces
 Gravity
 Capillary
 Electrostatic
 Magnetic
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Magnetically Directed Self-Assembly
 Objective
 To enable 3-D structures to be formed in parallel from a
heterogeneous mixture of parts of arbitrary size and shape
 Magnetics offers
 Bi-directional forces between components
 Attractive or repulsive forces between
components
 Controllable force and range (magnet
geometry, materials, and magnetization
direction)
 Favorable scaling to micro- and nanoscale
 Functionality in either wet or dry
environments
 Low-cost, batch-integrability
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Magnetic Self-Assembly
Part B (Flip Chip)
Array of
Magnetic
South Poles
Part C (Capacitor)
Solder
Bumps
Array of
Magnetic
North Poles
Part A (Circuit Board)
 Bonding structures much smaller than the size of the component
 “Lock and Key” pattern-matching mechanism
 Asymmetric and diverse patterns
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Magnetic Self-Assembly
 CoPt Hard Micromagnets
 Micromolding and electrodeposition
Deposit seed
layer
Substrate
Pattern
photoresist
20X
Plate magnets
Etch mold and
seed layer
Dice wafer
200X
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Magnetic Self-Assembly
 Magnetic Measurements of Film Properties
 Vibrating Sample Magnetometer (VSM)
Out of plane measurement
In plane measurement
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Magnetic Self-Assembly
 Force projections for CoPt micromagnets
Weight-force of a
5 mm x 5 mm x
0.5 mm chip
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Summary
 Magnetic Microdevices are rich in:
 Materials Development
 Design
 Fabrication
 Characterization
 Many opportunities for advancements in micromagnetics:
 Actuators
 Power Generators
 Self-Assembly
 Others: Sensor technologies
Integrated power inductors for power converters
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