Micropower Systems & Nanomagnetics
Dr. Saibal Roy : Head of Group
fromfromfromfrom
Fundamental Science/Fundamental Science/Fundamental Science/Fundamental Science/
EngineeringEngineeringEngineeringEngineering
totototo
MicroMicroMicroMicro----nanonanonanonano DevicesDevicesDevicesDevices
Innovation semantic waves
Textile Auto Computer Distributed
intelligence
IoTIoTIoTIoT
Nanotech
1853 1913 1969 2025 2061 2081
1771 1825 1886 1939 1997 2007
Industrial Revolution Information Revolution
1800 1853 1913 1969 2005 2025
Railway
The Internet of Things Scenario: 25 billion connected devices by 2020
Source: The Register, UK
Source: Mario Morales, IDC
Information
Batter
y
Energy Management and Storage
Energy Harvester
Ambient vibration
sources
Wireless Sensor Nodes (WSN)
WSN and Vibrational Energy Harvesting
Vibration
By 2020: 25 billion WSNs, $10 billion WSN market.
Application Environment
0.2-1g 1-10Hz & Impulse
0.01 – 1g, 2-100 Hz
0.2-1g, 2-50Hz
0.2 – 1g, 50Hz-
200Hz
0.01g,
240Hz
0.35g,
120Hz
Comparison of Different Transduction Methods
Different Transduction Methods
Electrostatic Piezoelectric Electromagnetic
These are based on changing
capacitances that plates will undergo
due to vibration. By placing charge on
the capacitor plates, the voltage will
change as the capacitance changes.
In Piezoelectric material, charge
displacement occurs when it is
strained. Thus a potential difference
is obtained. Thus electrical energy
can be produced.
EM generators are based on the
principle of Faraday’s Law of
Induction. When a conductor
moves through a magnetic field, a
potential difference is induced.
Thus power can be generated.
• High o/p voltage at low
operational voltage
• High impedance values > matching
network, design complexity, extra
power loss
• Active materials for fabrication
• High output Voltage
• Low output Current
• Do not need any extra
component like electret. No
external power supply is
needed.
• Output current is high but
voltage is low
Vibration Energy Harvesting
• Mechanical vibration energy converted into useable electrical energy.
• Systems are based on mass-spring-damper topologies.
• Transduction mechanisms rely on relative displacement of mover when frame is
excited by external vibration:
o Resonance optimal condition for maximum energy conversion
o Different transduction mechanisms: electrostatic, piezoelectric,
electromagnetic
7
(a.u.)
(a.u
.)
(Linear system)
Linear Generators on FR4
Linear Generator on FR4 (Standard PCB Material)
• Laser Micromachined FR4 resonator.
• NdFeb Permanent Magnets with soft magnets for
maximum flux linkage
• 468.13 μW of power under 0.3g acceleration for a
load of 2400 Ω.
Volume = 4.38 cm352 54 56 58 60 62 64 66 68
0
1
2
3
Op
en
Cir
cu
it V
olt
ag
e (
V)
Frequency (Hz)
0.05g
0.1g
0.3g
0.5g
52 54 56 58 60 62 64 66 6810-1
100
101
102
103
Lo
ad
Po
wer
( µµ µµW
)
Frequency (Hz)
0.5g
0.3g
0.1g
0.05g
• Low Young’s Modulus (21 GPa) – Useful for lowfrequency applications.
• Copper coils can potentially be routed.
• Low cost !!
Advantages of FR4:
D. Mallick & S. Roy, Sens. Act. A, 226, 154–162,
(2015).
1 cm
Resonant, Impulse, Shock Broadband, Random, Noise
2.5
Linear VEHWideband VEH
Vibration Sources – low frequency
Nonlinear Energy Harvesting
Nonlinearity introduced through modified stiffness of the devices
broader frequency response
10
Linear
Monostable
Bistable
α, β are constants
r - determines nature of nonlinearity
Copper Coil
NdFeB Magnets
FR4 Device Structure
1 cm
0 1 2 3 4
Displacement [mm]
Linear
Monostable
Bistable
Down
0.5mW peak power at 0.5g-
monostable
29 µW peak power at 0.5g-
bistable
0.5 V peak open circuit
voltage.
10 Hz bandwidth (15% of
peak power frequency)
Miniaturized Nonlinear Bistable & Monostable VEH ‒ (FR4)
Low Young’s Modulus
(22 GPa) – Useful for
low frequency
applications
Low cost !!
FR4 Advantages:
P Podder, A Amann, S Roy, Sensors and Actuators A: IEEE Trans Mechatronics, 2016
D Mallick, A Amann, S Roy, Smart Materials and Structures 24 (1), 015013, 2015
Bistable Monostable
Combined Effect – Multiple Nonlinearity
• Monostable and Bistable nonlinearity
combined in a single device
• Engineered potential energy for better
performance
• 107.2µµµµW and 1403 µµµµW at accelerations
of 0.2g and 1g respectively. UK Patent Filed (2015), PCT filed (2016): S. Roy, P. Podder, D. Mallick, A Amman
Soft magnet
Copper Coil
NdFeBmagnets
SOI springs
Perspex Casing
NdFeBmagnets
SOI springs
Silicon frame
Simulated deflection
1 mm
Transferring Technology to Silicon (SoI)
Fabricated VEH Device
1 mm 1 mm
Copper micro-coil
Power Power Power Power = = = = 0.5 0.5 0.5 0.5 µµµµWWWW
BW = BW = BW = BW = 20 Hz20 Hz20 Hz20 Hz
Acceleration = 0.5g
1
2
3
4
5
6
7
8
MEMS EM Energy Harvesters
Silicon On Insulator (SOI) Process Flow
Fabricated spring & integrated coil
SiSiSiSi SiOSiOSiOSiO2222
• SiSiSiSi devicedevicedevicedevice layerlayerlayerlayer –––– 50505050 μμμμmmmm
• BuriedBuriedBuriedBuried oxideoxideoxideoxide layerlayerlayerlayer –––– 3333 μμμμmmmm
Highly confidential, not to be circulated
MicroMicroMicroMicro----EMVEH using more SOI spring topologiesEMVEH using more SOI spring topologiesEMVEH using more SOI spring topologiesEMVEH using more SOI spring topologies
1 mm 1 mm 1 mm 1 mm
1 mm 1 mm 1 mm 1 mm
Silicon-on-insulator springs have been fabricated in the Central Fabrication Facility, Tyndall National
Institute using MEMS fabrication process.
Square and circular planar micro-coils and micro-magnets are to be used to assemble VEH.
Batch-fabrication of Integrated coils
Top view of fabricated Integrated coils
SEM image of fully fabricated silicon paddle with integrated
Cu coils
Process steps for Integrated coil fabrication
Micro-fabricated Cu Coils on Si
• Double layer electroplated planner coils• Coils used with micro and meso scale harvesters
DieDieDieDie ShapeShapeShapeShapeTrack Track Track Track Width Width Width Width
[[[[µµµµm]m]m]m]
Inter Inter Inter Inter tracktracktracktrack
Width [Width [Width [Width [µµµµm]m]m]m]NNNN
MeasuredMeasuredMeasuredMeasured
ResistanceResistanceResistanceResistance
ΩΩΩΩ
AAAA SquareSquareSquareSquare 8888 10101010 144144144144 192192192192
BBBB SquareSquareSquareSquare 10101010 8888 144144144144 155155155155
C1C1C1C1 SquareSquareSquareSquare 10101010 10101010 130130130130 140140140140
C2C2C2C2 SquareSquareSquareSquare 10101010 10101010 65656565 30303030
DDDD SquareSquareSquareSquare 12.512.512.512.5 12.512.512.512.5 104104104104 100100100100
EEEE SquareSquareSquareSquare 15151515 15151515 86868686 75757575
FFFF SquareSquareSquareSquare 15151515 10101010 104104104104 70707070
G1G1G1G1 CircleCircleCircleCircle 10101010 10101010 130130130130 111111111111
G2G2G2G2 CircleCircleCircleCircle 10101010 10101010 65656565 23232323
HHHH CircleCircleCircleCircle 12.512.512.512.5 12.512.512.512.5 104104104104 77777777
IIII CircleCircleCircleCircle 15151515 15151515 86868686 52525252
JJJJ CircleCircleCircleCircle 15151515 10101010 104104104104 61616161
2.8 x 2.8 mm2
Coil Properties
Track Widths /
inter track gaps
8-15µm
Aspect Ratio 1 2
Number turns up to 150
MEMS EM Energy Harvesters
Double Layer Cu Coil Process Flow
Fabricated CoilsCoil Cross-Section
Highly confidential, not to be circulated
19
Aim: Development of integrated high energy product nanostructured magnetic materials
Project: Simulation of micro-nano- patterns of Exchange-Coupled permanent magnets
Nanostructured, stress-free Co-rich CoPtP films for EMEH
• Co-rich Co80Pt20P films exhibit largeenergy products in their as-depositedstate.
• Do not require high temperatureannealing – CMOS process compatible.
• Electrodeposited using direct current(DC) and pulse-reverse (PR) platingtechniques.
• Co hcp hard magnetic phase with caxis perpendicular to the substratefor dc and in-plane for PR platedfilms.
• Stress relieving agent - Saccharin
• Improvement of 25% in the maximumcoercivity over DC plated films.
DC Plating PR Plating
Nanohole array on substrate (created at 160°C by Si stamp using 5N/m2 pressure) (Fig.a)
Gold seed layer on nanopattern (Fig.b)
Electroplated Ni45Fe55 on nanomodulated substrate at room temperature (Fig.c)
Angle dependent remanent magnetization (Mr) measured and plotted (Fig. d & e)
Anisotropy Control in Nano-patterned Continuous Magnetic Media
MFM phase images of dipoles.
An external field of 1000 Oe was applied in <110> direction before imaging. The
images were taken at a 50-nm distance from sample surface.
Steplike Hysteresis Hysteresis Hysteresis Hysteresis loop loop loop loop measured measured measured measured
from from from from thin thin thin thin nanomodulatednanomodulatednanomodulatednanomodulated sample (sample (sample (sample (a a a a
& c) & c) & c) & c) 150 nm and (b) 50 nm, shows 150 nm and (b) 50 nm, shows 150 nm and (b) 50 nm, shows 150 nm and (b) 50 nm, shows
metastable statemetastable statemetastable statemetastable state. . . .
Near Near Near Near zero zero zero zero remananceremananceremananceremanance, the dipoles , the dipoles , the dipoles , the dipoles
suddenly suddenly suddenly suddenly jump from jump from jump from jump from positive to positive to positive to positive to
negative negative negative negative value (c). value (c). value (c). value (c).
OOMMF OOMMF OOMMF OOMMF simulated picture simulated picture simulated picture simulated picture of of of of
magnetization magnetization magnetization magnetization configuration near configuration near configuration near configuration near
remanentremanentremanentremanent shows incomplete shows incomplete shows incomplete shows incomplete vortex vortex vortex vortex
(d)
Ref: Tuhin Maity, Shunpu Li, Lynette Keeney, Saibal Roy; Phys. Rev. B 86 (024438),
71, 2012
Tyndall Invested €1m
on advanced Magnetic Characterization Facility
SQUID (Superconducting quantum interference device) Magnetometer with variable temperature platform (1.8K-800K).Vendor- Quantum Design USA; Model- MPMS XL5.
Wide band (1MHz – 9 GHz) Permeameter for measuring complex permeability spectra. Vendor – Ryowa Electronics, Japan; Model – PMM-9G1.
On wafer (4” & 6”) hysteresis loop tracer. Vendor – SHB Instruments, USA; Model- MESA 200 HF.
SHB SQUID Ryowa