Micropower Systems & Nanomagnetics

Dr. Saibal Roy : Head of Group

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Fundamental Science/Fundamental Science/Fundamental Science/Fundamental Science/

EngineeringEngineeringEngineeringEngineering

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MicroMicroMicroMicro----nanonanonanonano DevicesDevicesDevicesDevices

Innovation semantic waves

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intelligence

IoTIoTIoTIoT

Nanotech

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Industrial Revolution Information Revolution

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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