Wrinkling 현상을 이용한 Biomimetic Surface 원리 및 응용

문 명 운문 명 운계산과학센터/미래융합기술연구소

한국과학기술연구원 (KIST)

Summer School, SNU, Aug 5th, 2008

� Introduction to wrinkle of Skin (or thin film) on soft substrate

Nano-structures on the surfaces

Wrinkles in the stiff skin on soft substrate

Wrinkles in multi-scale

� Wrinkle patterns and its application

Mechanism of wrinkling in thin films on soft substrates

Application of wrinkle in various aspects

- Evaluation of elastic moduli for the film or substrate

ContentsContents

- Evaluation of elastic moduli for the film or substrate

- Substrate for smart adhesion

- nano-/micro-size wrinkles for micro-fluidic system

Wrinkled hard skins induced by ion beam

� Hierarchical Structure in Wrinkle patterns

Hierarchically surfaces on lotus leaf

Hierarchical scale of wrinkle periods

Artificial hierarchy with nanowrinkle patterns on micro-fabricated patterns

� Summary & References

Instability of Wrinkles in technologyInstability of Wrinkles in technology

ContentsContents

� Introduction to wrinkle of Skin (or thin film) on soft substrate

Nano-structures on the surfaces

Wrinkles in the stiff skin on soft substrate

Wrinkles in multi-scale

� Wrinkle patterns and its application

Mechanism of wrinkling in thin films on soft substrates

Application of wrinkle in various aspects

- Evaluation of elastic moduli for the film or substrate- Evaluation of elastic moduli for the film or substrate

- Substrate for smart adhesion

- nano-/micro-size wrinkles for micro-fluidic system

Wrinkled hard skins induced by ion beam

� Hierarchical Structure in Wrinkle patterns

Hierarchically surfaces on lotus leaf

Hierarchical scale of wrinkle periods

Artificial hierarchy with nanowrinkle patterns on micro-fabricated patterns

� Summary & References

BuckleDelamination

w

0)(12

)(3

=′′−′′′′ xwhE

Txw

ff

a

w: displacement Ta: average force

Ef: plane strain modulushf: thickness of film

BendingStrain Energy

Work done by lateral force

Mechanism for thin film instabilityMechanism for thin film instability

Buckle/WrinklewithoutDelamination

M.W.Moon et al , Acta Mater. 2002

M. W. Moon et al, JMPS 2002

)(12

)(12

)(33

xphE

xwhE

Txw

ffff

m −=′′−′′′′

w: displacement Tm: membrane force

Ef: plane strain modulushf: thickness of film

p(x): normal tensile traction

Strain Energy lateral force

BendingStrain Energy

Work done by lateral force

Substrate deformation energy

)(12

)(12

)(33

xphE

xwhE

Txw

ffff

m −=′′−′′′′

BendingStrain Energy

Work done by lateral force

Substrate deformation energy

Wavelength/width

L

Wrinkle geometry : Width & HeightWrinkle geometry : Width & Height

w

( ) 3/1/08.4 sff EEhL ⋅=

Wavelength/width

E = elastic modulus

1// 0 −= cf eetW

e = induced strain

Amplitude/height

Bowden et al, Nature, 1997, Chen and Hutchinson, Scripta Mater. 2004

( )3

2

2

21

13

−

−=

ts

f

sfh

LEE

πν

ν

L

w

� Evaluation of Elastic modulus for thin film/skin

Effective way for intrinsic value for mechanical properties in thin film like

Application: Mechanical propertiesApplication: Mechanical properties

No stress, no influence from external forces!!!

Effective way for intrinsic value for mechanical properties in thin film likeUltra thin film, or hard polymers

−−

=

2

23

1

12

3 f

sff

sL

hEE

ννπ

� Evaluation of Elastic modulus for very soft Polymers

Intrinsic value for mechanical properties ofbiological materials, soft polymers

Application of wrinkle patternsApplication of wrinkle patterns

1. Micro-/nano- patterning

2. Evaluation of elastic modulus for very thin films2. Evaluation of elastic modulus for very thin films

3. Evaluation of elastic modulus for very thin polymers on water

4. Application for smart adhesion

5. Bridging micro-channals using nanochannels for protein precondensation

Systems: Skin: Pt Substrate: PDMS Strain: thermal expansion � Patterning in Microscale

Application: Wrinkle PatterningApplication: Wrinkle Patterning

Bowden et al, Nature 1998

Systems: Skin: UV/O Substrate: PDMS Strain: Pre-stretching � Measurement of elastic modulus for PDMS

Application: Measurement of ModulusApplication: Measurement of Modulus

Stafford et al, Nature Materials 2004

Systems: Skin: PS Substrate: Water Strain: surface tension � Measurement of ultra thin polymer film

Application: Measurement of Modulus(2)Application: Measurement of Modulus(2)

Science, 2007

Application: Smart adhesionApplication: Smart adhesion

Surface Wrinkles for Smart Adhesion, Chan et al, Adv. Mater. 2008

Application: Smart adhesionApplication: Smart adhesion

Application: Wrinkle nanochannelsApplication: Wrinkle nanochannels

a) b)

Application: Wrinkle nanochannelsApplication: Wrinkle nanochannels

c)

Chung, Lee, Moon et al Advanced Materials 2008

Wrinkled Hard SkinsWrinkled Hard Skins

- Mechanism and Patterning methods -

Limitation for wide application with previous method:- Complicated steps to make wrinkle (deposition and external force) - Not easy to fabricate local region and desired direction!!!- Size of wrinkle wavelength is not controllable.

Wrinkled Hard Skin on Soft PolymersWrinkled Hard Skin on Soft Polymers

Wrinkle with ion beam: One step fabrication methodof wrinkle pattern in desired region over various sizes

Moon, Lee, Sun, Oh, Ashkan, Hutchinson, PNAS 2007

Why is the Wrinkled Skin?Why is the Wrinkled Skin?

Ion beam/plasma irradiation induced a wrinkled skin soft polymer, PDMS (polydimethylsiloxane)

-Selective areas of PDMS – localized fluidic patterns-Nanoscale wrinkle geometries: 40~2000nm in wavelength

10~1000nm in amplitude

Wrinkled Hard SkinsWrinkled Hard Skins

Moon et al, PNAS 2007, Scripta Materialia 2007Chung et al, Advanced Materials 2008

Application for cell culturing templates and nano-fluidic channelsbut limited in throughput for mass production.

Wrinkles on polymer by FIBWrinkles on polymer by FIB

PDMS – Elastomer vs cross linker = 15:1,cured at 80℃ 1hour

FIB (HRFIB/SEM, nova200, FEI)30KeV, 1pA~20nA.

Fluence range, 1013~1016 ions/cm2 , controlled by the current, exposing time and exposing area

II--Beam NO IBeam NO I--BeamBeam

Wrinkle by FIB : MechanismWrinkle by FIB : Mechanism

PDMS

FIB

Exposed region

skin UVO, or Plasma, E/I-beam: a stiff skin� Cross-linker altered � From PDMS to Silica like material

Ouyang e tal (2000) & Efimenko et al (2005)

Stiff skin

100times stiffer!

PDMS

FIB

Exposed region

skin Compression by ion beam on glassy metalsor oxide layer

� Ion bombardment or

� Anisotropic deformation (in-plane compressive strain)

Klaumunzer & Schumacher (1983)Kim et al (2006), Otani et al (2006)

In-plane stress

Wrinkle formed in nanoscaleWrinkle formed in nanoscale

200nm200nm

Accelerating voltage: 5keV

~40nm

20㎛20㎛

Accelerating voltage: 30keV

~450nm

• HR TEM mapping EDS analysis

Chemical composition: TEMChemical composition: TEM

Oxygen

Carbon

500nm

wrinkle

Silicon

Thickness of a new stiff layer

~ 25-30nm

Pt

MaskMask--less Patterning Methodless Patterning Method

• Bitmap Image For FIB mask

Directed assembled channels; ‘S’

‘N’ ‘U’

Direct writing of nanoDirect writing of nano--channelchannel

USA patent pending, PNAS 2007

Microfluidic channelsMicrofluidic channels

Bitmap images

Focused Ion beam

• Bitmap Image

for a FIB virtual mask

Moon et al, Scripta Materialia (2007) Nano-micro fluidic path

Patterning

ContentsContents

� Introduction to wrinkle of Skin (or thin film) on soft substrate

Stress induced instability in hard film and soft films

Wrinkles in the stiff skin on soft substrate

� Wrinkle patterns and its application

Mechanism of wrinkling of thin films on soft substrates

Application of wrinkle in various aspects

- Evaluation of elastic moduli for the film or substrate- Evaluation of elastic moduli for the film or substrate

- Substrate for smart adhesion

- nano-/micro-size pattern formation on the surfaces

Formation of wrinkled hard skins by ion beam

� Hierarchical Structure in Wrinkle patterns

Hierarchically surfaces on lotus leaf

Hierarchical scale of wrinkle periods

Artificial hierarchy with nanowrinkle patterns on micro-fabricated patterns

� Summary & References

Hierarchical Mode in WrinklesHierarchical Mode in Wrinkles

1. 1-D: Hierarchical wrinkle patterns from UVO treatment on soft polymer

2. 2-D: Wrinkle modes evolved from ion beam bombardment

3. 3-D: Multi-scale structure fabricated with top-down and bottom-up method

Hierarchical Structure in NatureHierarchical Structure in Nature

Over 200 PlantsHierarchical morphologies

Non-wettingSelf-cleaning

Hierarchical Structures in 1Hierarchical Structures in 1--D WrinklesD Wrinkles

UVO treated PDMS surface

K. EFIMENKO, et al, Nature Materials 2005

Hierarchical Structures in 1Hierarchical Structures in 1--D WrinklesD Wrinkles

Sorting the particles mixed in multi-scales

Microsize silica particles(3 and 10 um) by microsize wrinkle patterns

Nano-size (70nm) by nanowrinkled patterns

• Single scan of ion modeHierarchical

Hierarchical Structures in 2Hierarchical Structures in 2--D WrinklesD Wrinkles

Herringbone

Straight

F = 2X1013

N = 1

F = Fluence, ions/cm2N = number of scan

Hierarchical Structures in 2Hierarchical Structures in 2--D WrinklesD Wrinkles

F = 2X1013

N = 15

F = 2X1013

N = 20Double scale

Wavelength!!!

F = 1X1013

N = 1

F = 5X1013

Hierarchical Structures in 2Hierarchical Structures in 2--D WrinklesD Wrinkles

F = 5X1013

N = 1

F = 7X1013

N = 1 Multiple scale

in wavelength!!!

F = Fluence, ions/cm2N = number of scan

� Wrinkles on natural surfaces Body, mountain, organs, polymers, metal filmsMulti-scale structures from Km to nm

� Mechanism of wrinkle and its applicationElastic modulus differences and lateral strain

� wavelength and amplitude with thickness of film

Applications of wrinkle : � Evaluation method of moduli of ultrathin layers or soft materials� Patterned templates for micro-/nano- biology

SummarySummary

� Patterned templates for micro-/nano- biology� Nano channels for fluidic application: protein precondensation� Dry/wet adhesives for soft systems

� Wrinkled hard skin with focused ion beamHard skin with wrinkle by ion beam bombardment

� No deposit of skin/thin film, No applied stress� Localized and selected area patterning

� Hierarchical mode for wrinkling morphologiesStraight, herringbone, nested herringbone with multi-scale widthsArtificial fabrication of nano-micro multi-scale surface morphologies

ReferencesReferences

[1] M.-W. Moon, S. H. Lee, J.-Y. Sun, K. H. Oh, A. Vaziri, and J. W. Hutchinson, Proc. Natl Acad. Sci. USA 104 (2007) 1130.

[2] M.-W. Moon, S. H. Lee, J.-Y. Sun, K. H. Oh, A. Vaziri, J. W. Hutchinson, Scripta materialia, 57 (2007) 747-750.

[3] S. Chung, J. H. Lee, M.-W. Moon, J. Han, R. D. Kamm, Advanced Materials (2008. 07).

[4] J Huang, M Juszkiewicz,W H. de Jeu, E Cerda,T Emrick, N Menon, T P. Russell, Science, 317(2007) pp. 650 – 653

[5] K. Efimenko, M. Rackaitis, E. Manias, A. Vaziri, L. Mahadevan, J. Genzer, Nature Mater. 4 (2005) 1.

[6] J. El-Ali , P.K. Sorger, K.F. Jensen, Nature 442 (2006) 403. [6] J. El-Ali , P.K. Sorger, K.F. Jensen, Nature 442 (2006) 403. [7] E.P. Chan and A.J. Crosby, Adv. Mater. 18 (2006) 3238.[8] C. Harrison, C.M. Stafford, W. Zhang, A. Karim, Appl. Phys. Lett. 85

(2005) 4016.[9] J. Genzer, J. Groenewold, Soft Matter. 2 (2006) 310.[10] G. Reiter, Phys. Rev. Lett. 68 (1992) 75. [11] P.J. Yoo,K.Y. Suh, S.Y. Park, H.H. Lee Adv. Mater. 14 (2002) 1383. [12] N. Bowden, S. Brittain, A.G. Evans, J. W. Hutchinson, G.M. Whitesides,

Nature 393 (1998) 146.[13] S.P. Lacour SP, S. Wagner,Z. Huang, Z. Suo Appl. Phys. Lett. 82

(2003) 2404.[14] T. Ohzonoa, M. Shimomuraa, Phys. Rev. E 73 (2006) 040601.

KIST - 이광렬박사,이진우박사, Dr. Sk. Faruque Amhed

SNU - 오규환교수, 선정윤, 이상훈, 허은규김호영교수, 차태곤, 서갑양교수, Yudi Rahmawan

AcknowledgmentsAcknowledgments

Collaborators

Harvard – Prof. John W. HutchinsonDr. Ashkan Vaziri

MIT – Prof. Kamm, Prof. Han, 정석 박사, 이정훈박사

Funding from- 21st Century Frontier R&D Programs

of Center for Nanostructured Materials Technology - Korea Research Foundation

Thanks !!!

Please ask questionsfor further details!!!for further details!!!