Special TopicElectroactive Polymers (EAPs)

Prof. Seung Tae CHOI ( )

22 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Why are Electroactive Polymers (EAPs)

Transducers are a critical part ofMEMS/MOEMS devicesEAPs have unique characteristicsand bring new possibilities

MECHANICAL WORKENERGY

(ELECTRICAL)

EAPE W

ACTUATOR

GENERATOR OR SENSOR

What’s wrong with current MEMS actuators?» Electrostatic – low forces, small

scale only (high tolerance), stiction» Electromagnetic – inefficient at small

scales» Piezoelectric – small strain, high

tolerances, more complex fabrication, Pb

» Thermal and Bubble – inefficient, not reversible (actuator only), relatively slow, proportional control difficult

» Shape Memory Alloy – inefficient, not reversible (actuator only), relative slow, complex fabrication, proportional control difficult

33 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Many Types of EAPs

Artificial Muscle”

Electrostrictive Polymer

Dielectric Elastomer

IPMC

Conducting Polymers

GelsThermal and Others

Nanotubes

44 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Electroactive Polymer (Artificial Muscle)

+ + + + + + + + + + +

Electronic EAP Ionic EAP

Electroactive Polymers

55 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Ionic EAPs

Ionic Polymer Gel

Conductive Polymers and IPMC

66 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Electronic EAPsElectrostrictive polymers

Piezoelectric polymers

77 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

(DIELECTRIC ELASTOMERS)

88 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Dielectric Elastomer Actuators

E

EmaxEmax

99 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

V

Dielectric Elastomer Actuators

Desirable characteristics

But

110 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Artificial Muscle for Micro Robots?

EAPs can behave a lot like a muscleMuscle is a spring damper systemand sensor in addition to a motor

http://www.britannica.com/science/skeletal-muscle

111 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Bioinspired Electroactive Butterflies

112 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

(FLUORINATED FERROELECTRIC POLYMERS)

-phase

-phase

H

HH

FF H

F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

4.62 A

5.16 A

H

FF

H H

FF

H H

FF

H H

FF

H H

FF

H

FF

Electricfield

Heating/cooling

113 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Ferroelectric PolymersPVDF = Polyvinylidene fluoride & P(VDF-TrFE) = Poly(vinylidenefluoride-trifluoroethylene)Ferroelectric behavior due to permanent electric dipoles

-phase

-phase

http://canopus.physik.uni-potsdam.de/research/limm/pvdfspin.gif

VDF TrFE

H

C

H

C

F F

C

H

C

F F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

4.62 A

5.16 A

H

FF

H H

FF

H H

FF

H H

FF

H H

FF

H

FF

Melt

Solution

Poling at very high E

Annealing at very high P

Ultradrawing at high T

Drawing at low T

Annealing at high T

All TsEpitaxially on KBr

High P

(Possibly at high T?)High T

High P

MCB/DMF,Cyclohexanone

DMF, DMA, or DMSO

Cyclohexanone

Annealing at high T

(Possibly by annea

ling at high P)

Poling at very high E

Microstructure of PVDF or P(VDF-TrFE)

226 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

(RELAXOR FERROELECTRIC POLYMER ACTUATORS)

P

PP

P

P PPP

PP

P : Nanoscale paraelectric domain

: Nanoscale ferroelectric domain

Electric field off Electric field on

P

P P

P

227 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Relaxor Ferroelectric Polymers

Polarizationhysteresis

P(VDF-TrFE-CFE) terpolymer actuator: The large strains associated with the conformation changes between the polar- and non-polar conformations in PVDF-based ferroelectric polymer can be used of to generate high electrostrictive strain

VDF TrFE CFE

H

C

H

C

F F

C

H

C

F F

F

-phase

-phase

H

HH

FF H

F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

H

HH

FF H

F

F

4.62 A

5.16 A

H

FF

H H

FF

H H

FF

H H

FF

H H

FF

H

FF

H

C

H

C

F Cl

Electricfield

Heating/cooling

P

PP

P

P PPP

PP

P : Nanoscale paraelectric domain

: Nanoscale ferroelectric domain

Electric field off

Electric field on

P

P P

P

229 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Piezotech FC™ & RT™ in Actuators

331 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Biomimetic Varifocal Lens

Varifocal liquid lens

Hydraulic pressure eyesImaging system Human eye Cetacean eye

Eye shape Spherical eyecup Hemispherical eyecup

Lens Elliptic lens Spherical lens

Major optical power

Convex outer surface of cornea Strongly convex (spherical) lens

Change of focus

Change of the lens shape by ciliary muscle

Axial displacement of the lens due to changes in intraocular

pressure

Anatomy

Natural imaging systems

https://www.youtube.com/watch?v=bA-jDk3-Mgs

334 SCHOOL OF MECHANICAL ENGINEERINGLECTURER: PROF. SEUNGTAE CHOI

Operation of Varifocal Lens

• Wafer-Level Process: World-First• Thickness < 0.6 mm: World-Best