micro/nano mechanical systems lab –class#5 · finger motions (chip-size), footsteps (palm-size)...

Microsystems LaboratoryUC-Berkeley, ME Dept.

1Liwei Lin, University of California at Berkeley

Micro/Nano Mechanical Systems Lab – Class#5

Liwei Lin

Professor, Dept. of Mechanical Engineering Co-Director, Berkeley Sensor and Actuator CenterThe University of California, Berkeley, CA94720

e-mail: [email protected]://www.me.berkeley.edu/~lwlin



Outline

Review – Energy Harvesters Intro - MicroRobots

Microsystems LaboratoryUC-Berkeley, ME Dept.Power Sources for

Electronics & Sensors in IoT ?

“IoT will consist of almost 50 billion objects by 2020”.—— Dave Evans, Cisco

2020

1. Sensors2. Power3. Wireless Comm.


Energy from Mechanical SourcesThere are many available mechanical energy sources in the real world, ranging from human motion, water falls, ocean waves, bridge/building/train motion, wind, cars, sound/acoustics … There have been several research reports on mechanical energy harvesters.Source Frequency Generated Power Reference/Source

Human Motion

<5 Hz ~100 W for a 65 kg Man 1. Wang, Z. et al. ACS Nano 2013, 9533.2. Brooks, G. et al. Exercise Physiology: Human Bioenergetics and Its Applications. McGraw-Hill, ,2005

Water Drop/Rain

<5 Hz 20 MJ or 5.5 kWh for 1000 kg form 2000 m

3. Lin, Z. et al. Angew. Chem. Int. Edi. 2013, 125, 12777.4.http://large.stanford.edu/courses/2010/ph240/harting2/

Ocean Waves

<10Hz 2,640 TWh/Year All Around the Word

5. Zi, Y. et al. ACS Nano, 2016, 10, 4797. 6. https://www.boem.gov/Ocean-Wave-Energy/

Bridge/building

1-40 Hz Acceleration from 0.01 to 3.8g; Power Density 0.01 to 9539 μW/cm3

7. Abu Riduan, M. et al. J. Semicond. 2012, 33, 074001.8. Khan, F. et al. Shock and Vibration, 2016, 1340402.

Train/Rail <20 Hz ~ 2.5 mW/cm3 for a 120 km/h Train

9. Jin, L. et al, Nano Energy, 2017, 38, 185.10. Paul, C. et al. J. Bridge. Eng. 19. 04014034.

Air Flow/Wind

<100 Hz ~ 800 TWh/Year All Around the Word

11. Wang, Z. et al, Angew. Chem. Int. Edi. 2012, 51, 11700.12. https://en.wikipedia.org/wiki/Wind_power

Vehicle Engine

<300 Hz 0.1-1 mW/cm2 for a Honda Car

13. Yang, J. et al, IEEE T. Contr. Syst. T. 2001, 9 (2), 295.14. Chen, J. Et al. Adv. Mater. 2013, 25, 6094.

Sound/Acoustic Noise

20 Hz-20 kHz

0.003 μW/cm2 for 75 dB0.96 μW/cm2 for 100 dB

15. https://en.wikipedia.org/wiki/Audio_frequency16. Yildiz, F. J. Tech. Study, 2009, 35, 40.

Microsystems LaboratoryUC-Berkeley, ME Dept.Example: Human Motions

There are significant mechanical energy sources available for harvesting in human activities using different sizes for optimal energy collections, such as: finger motions (chip-size), footsteps (palm-size) and body motions (large size) using potential various energy conversion mechanisms, including piezoelectric, triboelectric, electrets …

Human Motion Generated Mechanical Power

Ideal Converted Electrical Power

Ideal Converted Electrical Energy

Blood Flow 0.93 W 0.16 W 0.16 JExpiration 1 W 0.17 W 1.02 JBreathing 0.83 W 0.14 W 0.84 JUpper Limb Motion 60 W 10-30 W 10.2 JFinger Motion 6.9-19 mW 1.2-3.3 mW 226-406 μJWalking Motion 67 W 11-39 W 18.6 J

chip

chippalm/large

Palm/largelarge

chip

Microsystems LaboratoryUC-Berkeley, ME Dept.MEMS Integrated Harvesters

Dev

ice

Size

Peak Output Power

cm2

mm2

nWPiezoelectric

Chip-scale Integrated

Integrated Sensors

Integrated Circuits

1. Integrated CMOS process2. High volume low cost fabrication3. Materials & process development4. Design & application demos

W


Fully CMOS Integrated Process

p+p+

N well

SiO 2

SiO 2 SiO 2p+ Poly

Top Electrode

SiO 2

Passivation layer

Opening

Energy Harvester(Mo/AlN/Mo)

Si-substrate

Bottom Electrode

Proof Mass

Piezoelectric Material (AlN)

“Beyond Microelectronics”Current state-of-art microelectronics are powered by external power sources. On-chip power sources such as MEMS energy harvesters can extend the chips to another dimension beyond the current capabilities. CMOS is the most widely utilized process to be utilized here.

Material and Process - I

Microsystems LaboratoryUC-Berkeley, ME Dept.Material and Process - II

Multilayered piezoelectric flexible energy harvester using interleaved electrodes a. Multiple layers of 20 µm piezoelectric polymer (e.g., P(VDF-TrFE)) sandwiched with metal electrodesb. Development of novel piezoelectric polymer with additives to form polar phase with enhanced piezoelectricityc. Enhanced output power by electrically parallel-connection and impedance matched designd. Low-temperature, low-cost and scalable process for IOT applications


Flexible Piezoelectric TransducerPart I:

9


10

Piezoelectricity

Active Effect

Negative EffectQuartz

Electrical Dipoles

Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress.

Microsystems LaboratoryUC-Berkeley, ME Dept.Piezoelectric Materials

Single Crystal materials: Zinc Oxide (ZnO), Quartz, Barium Titanate (BaTiO3), etc.Polycrystal materials: There is no piezoelectricity before poling. Piezoceramics (PZT), Piezopolymers (PVDF), etc.

E

Before poling In poling After poling

I II III

Electrical Poling: Applying high electrical field to dipoles

11


Example: ZnO Nanowires

Z. L. Wang, J. Song, Science 2006, 312, 242. 12


Transport is governed by a metal-semiconductor Schottky barrier for the PZ ZnO NW

13


Electromechanically

coupled discharging

process of aligned

piezoelectric ZnO

NWs observed in

contact mode.

14


Piezoelectricity of Monolayer MoS2

W. Wu, et al, Nature 2014, 514, 470.15

Second-Harmonic Generation(SHG)


01/30 Tuesday 1pm: Harrison Khoo, Ian Connett，Martin Xu

01/30 Tuesday 2pm: Dan Xu, Vedang Patankar

01/30 Tuesday 4pm: Margann Rui, Tiffany, Vatsal

01/31 Wensday 3pm: Amruth,Marina Rizk, Lujain Alobaide, Nate

02/01 Thursday 1pm: Neil, Junpyo Kwon

Lab Experiment ScheduleEtcheverry Hall 1113


Flexible Electrostatic TransducerPart II:

17


An electret is a piece of dielectric material exhibiting a quasi‐permanent electric charge

Electrets

J. A. Malecki, PRB 1999, 59, 9954

Even hundreds of years

18

Microsystems LaboratoryUC-Berkeley, ME Dept.Corona Discharge

[ C C ]

F F

F F

n

Corona charge

A

-15 kV

Electret

Needle

Electrode

Electret material: Teflon (PTFE)

Charges injection

G. M. Sessler, Electrets(2nd ed), Berlin: Springer‐Verlag, 198719


20

Surface Potential Detection

0 5 10 15 20 25 300

-1

-2

-3

Surf

ace

Pote

ntia

l (kV

)

Time (Day)

PE

0 5 10 15 20 25 300

-1

-2

-3

-4

Surf

ace

Pote

ntia

l (kV

)

Time (Day)

pp

PP

0 5 10 15 20 25 300

-2

-4

-6

-8Su

rfac

e Po

tent

ial (

kV)

Time (Day)

PTFE

0 5 10 15 20 25 300

-2

-4

Surf

ace

Pote

ntia

l (kV

)

Time (Day)

PET

0.1-1 mC/m2

Microsystems LaboratoryUC-Berkeley, ME Dept.Example: Paper-Based

21

Paper Metal (M) Polymer

Paper

Coating P@Pre-Paper

Assembling

Ⅱ Ⅲ ⅣⅠ

100 μm 500 nm

Evaporate M

Q. Zhong & J. Zhong et al., Energy Environ. Sci., 2013, 6, 1779

Charge Injection

PTFE


22

Example: Cloth-Based Shirt

S. Li, Q. et al, ACS Applied Materials & Interfaces 2015, 7, 14912.


Challenges


0.0 0.1 0.2-6

-3

0

3

Cur

rent

(A)

Time (s)0 2 4

0

1

2 Experimental Fitting

Forc

e (N

)

Lateral Distance (mm)

SampleMeter

/2 2 6

03.46 10

T

eW I Rdt J

/2 3

01.07 10

A

FW Fds J

100% 0.32%e

F

WW

Efficiency:

Input mechanical energy:

Output electricity:

I: Energy Conversion Efficiency

Measurement system

24


25

II: Output Power

Larger Power, More Applications!

Improving the Charge Density of the Electret and the Device Structure!

Wang, Z. L.; Angew. Chem. Int. Edit. 2012, 51, 11700.


26

BOPP PET

PTFEPI PE

PDMS

FEP

0

-2

-4

-6

-8

Surf

ace

Pote

ntia

l (kV

)

Original Recovering

III: Package (against water)

Electret Film against Harsh Environment is a challenge!


27

Microsystems LaboratoryUC-Berkeley, ME Dept.Summary

Three Typical Application FieldsAssistance of Internet of Things

37

WearableElectronics

Self-poweredSensors

Energy Harvesting

W. Li and J. Zhong et al, Adv. Funct. Mater., 2015, 26,1964


Intro to MicroRobots


Flying Insects

Artificial Flying Insects

Category

Nano Hummingbird Robotic Insect Microrobot

Size 15cm 3cm 1.5cm

Status Autonomous flight Tethered flight Flapping motion

Actuator DC motor PZT ElectrostaticM. Karpelson, G. Y. Wei, R. J. Wood, "A review of actuation and power electronics options for flapping-wing robotic insects,"

2008 Ieee International Conference on Robotics and Automation, Vols 1-9, pp. 779-786, 2008.


Actuators

Actuators for Artificial Flying Insects

M. Karpelson, G. Y. Wei, R. J. Wood, "A review of actuation and power electronics options for flapping-wing robotic insects," 2008 Ieee International Conference on Robotics and Automation, Vols 1-9, pp. 779-786, 2008.

Actuator

DC motor PZT Electrostatic

AdvantageHigh drive efficiencyDC power electronics

Linear motionHigh power density

High drive efficiencyMiniaturization (easy)

DisadvantageRotary motion

Miniaturization (hard)AC power electronics

Low efficiencyPull-in effectLow lift force

Vibration Forced Vibration (Flapping Frequency =Input Signal )


Inspiration from Nature

Insects Muscle’s Vibration

Flapping signal ≠ Neural signal Self-excited vibration

R. Josephson, J. Malamud, D. Stokes, "Asynchronous muscle: a primer," J. Exp. Biol., vol. 203, pp. 2713-2722, 2000.


Research Concept and Approach

Electrostatic Actuation

Electrostatic actuator Our actuator

Advantages

Linear motionMaintain

the advantages by using electrostatic actuation.

High drive efficiency

Ease of miniaturization

Disadvantages

Pull-in effectOvercome

the disadvantages by using self-excited vibration.

AC power electronics

Low lift force


Self-excitation

Self-excited Vibration of Beam

Experimental setup Insulated base Metal beam DC power sourceVibration course Electrostatic induction No Pull-in effect Charging and discharging

Xiaojun Yan, Mingjing Qi, Liwei Lin, An autonomous impact resonator with metal beam between a pair of parallel-plate electrodes, Sensors & Actuators: A. Physical , pp. 366-371, 2013.


Operating Principle

Vibration Course of the Beam (top view)

Xiaojun Yan, Mingjing Qi, Liwei Lin, An autonomous impact resonator with metal beam between a pair of parallel-plate electrodes, Sensors & Actuators: A. Physical , pp. 366-371, 2013.

Structure parameters Materials: gold bonding wire Length: 10.5mm Diameter: 25.4μm DC voltage: 1100VVibration parameters Amplitude: 4.5mm Frequency: 80Hz


Actuator Design

Configuration

Flapping wing assembly: Four parallel beams and two wings Parallel metal beams: Enhance the driving force Two wings: Extracted from honey bees Fulcrum bars with oval holes: Allow the beams to rotate

Microsystems LaboratoryUC-Berkeley, ME Dept.Flipping & Rotation

Rotational Fulcrum Bars

Electrostatic induction Incline to electrodes Contact and charged Reverse direction Flap and rotation


Experimental Setup

Experimental Tests


Experimental Setup

Lift Force


Comparisons with Insects

Flapping Motion

Realinsect

Ouractuator


Video Demo

Flapping Motion


Experimental Results

Operation Frequency Characterizations

Decrease with gap distance d0


Effects of Electrode Gap Distance

Flapping Angle Characterizations

Increase with d0 under high voltage Decrease with d0 under low voltage


FLift

Lift Force vs Gap Distance

Lift Force Characterizations

Increase with d0 under high voltage Decrease with d0 under low voltage


Vertical Lift-Off Setup

Vertical Takeoff

U-shape rail: Allow the assembly to move upward Extended electrodes: Provide continuous driving force

Upward speed: 2.2mm/s Frequency: 70Hz


Visual Demonstration of Lift Force

Video Demo


Design to Enhance Wing Rotation

Structure Optimization

One oval hole Two holes setup


Video Demo

Enhanced Rotational Motion


Conclusion

The actuator can be excited into resonance with frequency of 50-70Hz by simply DC power source.

The actuator can drive two insect wings into reciprocation with flapping amplitude up to 48.5.

The flapping wing assembly can generate effective lift force (up to 3.1mg) high enough to result in self-lifting.

Our next work aims at further enhancing the lift force and reducing the total weight, for the purpose of realizing the takeoff of the whole actuator.

micro/nano mechanical systems lab –class#5 · finger motions (chip-size), footsteps (palm-size)...

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