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1 Wrinkling 현상을 이용한 Biomimetic Surface 원리 및 응용 문명운 계산과학센터/미래융합기술연구소 한국과학기술연구원 (KIST) Summer School, SNU, Aug 5th, 2008

2 Contents 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 - 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

6 Instability of Wrinkles in technology

9 Contents 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 - 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

rk done by lateral force M.W.Moon et al, Acta Mater. 2002 M. W.

12 Mechanism for thin film instability Buckle Delamination w w: displacement Ta: average force Ef: plane strain modulus hf: thickness of film 12Ta w ( x) w ( x) = 3 E h f f 0 Bending Strain Energy Work done by lateral force M.W.Moon et al, Acta Mater M. W. Moon et al, JMPS 2002 Buckle/Wrinkle without Delamination 12Tm 12 w ( x) w ( x) = p( x) 3 3 E h E h f f w: displacement Tm: membrane force Ef: plane strain modulus hf: thickness of film p(x): normal tensile traction f f Bending Strain Energy Work done by lateral force Substrate deformation energy

13 Wrinkle geometry : Width & Height L w 12Tm 12 w ( x) w ( x) = p( x) 3 3 E h E h f f f f Bending Strain Energy Work done by lateral force Substrate deformation energy Wavelength/width L= h ( ) E / E 1/ f f s Amplitude/height W E = elastic modulus / t = e / e 1 f 0 c e = induced strain Bowden et al, Nature, 1997, Chen and Hutchinson, Scripta Mater. 2004

14 ( ) = t s f s f h L E E π ν 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 properties Application: Mechanical properties No stress, no influence from external forces!!! Effective way for intrinsic value for mechanical properties in thin film like Ultra thin film, or hard polymers = f s f f s L h E E ν ν π Evaluation of Elastic modulus for very soft Polymers Intrinsic value for mechanical properties of biological materials, soft polymers

16 Application of wrinkle patterns 1. Micro-/nano- patterning 2. 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

17 Application: Wrinkle Patterning Systems: Skin: Pt Substrate: PDMS Strain: thermal expansion Patterning in Microscale Bowden et al, Nature 1998

18 Application: Measurement of Modulus Systems: Skin: UV/O Substrate: PDMS Strain: Pre-stretching Measurement of elastic modulus for PDMS Stafford et al, Nature Materials 2004

19 Application: Measurement of Modulus(2) Systems: Skin: PS Substrate: Water Strain: surface tension Measurement of ultra thin polymer film Science, 2007

20 Application: Smart adhesion Surface Wrinkles for Smart Adhesion, Chan et al, Adv. Mater. 2008

21 Application: Smart adhesion

23 Application: Wrinkle nanochannels

24 Application: Wrinkle nanochannels a) b) c) Chung, Lee, Moon et al Advanced Materials 2008

25 Wrinkled Hard Skins - Mechanism and Patterning methods -

direction!!! - Size of wrinkle wavelength is not controllable.

26 Wrinkled Hard Skin on Soft Polymers 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. Wrinkle with ion beam : One step fabrication method of wrinkle pattern in desired region over various sizes Moon, Lee, Sun, Oh, Ashkan, Hutchinson, PNAS 2007

27 Why is the Wrinkled Skin?

Wrinkled Hard Skins Ion beam/plasma irradiation induced

(polydimethylsiloxane) -Selective areas of PDMS

geometries: 40~2000nm in wavelength 10~1000nm in

2007 Chung et al, Advanced Materials 2008 Application

28 Wrinkled Hard Skins 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 Moon et al, PNAS 2007, Scripta Materialia 2007 Chung et al, Advanced Materials 2008 Application for cell culturing templates and nano-fluidic channels but limited in throughput for mass production.

29 Wrinkles on polymer by FIB PDMS Elastomer vs cross linker = 15:1, cured at 80 1hour I-Beam NO I-Beam FIB (HRFIB/SEM, nova200, FEI) 30KeV, 1pA~20nA. Fluence range, ~10 16 ions/cm 2, controlled by the current, exposing time and exposing area

30 Wrinkle by FIB : Mechanism FIB skin Exposed region PDMS Stiff skin UVO, or Plasma, E/I-beam: a stiff skin Cross-linker altered From PDMS to Silica like material 100times stiffer! Ouyang e tal (2000) & Efimenko et al (2005) FIB skin Exposed region PDMS In-plane stress Compression by ion beam on glassy metals or oxide layer Ion bombardment or Anisotropic deformation (in-plane compressive strain) Klaumunzer & Schumacher (1983) Kim et al (2006), Otani et al (2006)

31 Wrinkle formed in nanoscale Accelerating voltage: 5keV ~40nm 200nm 200nm Accelerating voltage: 30keV ~450nm 20 μm 20 μm

32 Chemical composition: TEM HR TEM mapping EDS analysis Oxygen Carbon wrinkle Pt Silicon 500nm Thickness of a new stiff layer ~ 25-30nm

33 Mask-less Patterning Method Bitmap Image For FIB mask

34 Direct writing of nano-channel Directed assembled channels; S N U USA patent pending, PNAS 2007

35 Microfluidic channels Bitmap Image for a FIB virtual mask Focused Ion beam Bitmap images Moon et al, Scripta Materialia (2007) Nano-micro fluidic path

36 Patterning

37 Contents 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 - 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

38 Hierarchical 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

39 Hierarchical Structure in Nature Over 200 Plants Hierarchical morphologies Non-wetting Self-cleaning

41 Hierarchical Structures in 1-D Wrinkles UVO treated PDMS surface K. EFIMENKO, et al, Nature Materials 2005

42 Hierarchical Structures in 1-D 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

43 Hierarchical Structures in 2-D Wrinkles Single scan of ion mode Hierarchical Herringbone Straight

44 Hierarchical Structures in 2-D Wrinkles F = 2X10 13 N = 1 F = Fluence, ions/cm2 N = number of scan F = 2X10 13 N = 15 F = 2X10 13 N = 20 Double scale Wavelength!!!

45 Hierarchical Structures in 2-D Wrinkles F = 1X10 13 N = 1 F = 5X10 13 N = 1 F = Fluence, ions/cm2 N = number of scan F = 7X10 13 N = 1 Multiple scale in wavelength!!!

46 Summary Wrinkles on natural surfaces Body, mountain, organs, polymers, metal films Multi-scale structures from Km to nm Mechanism of wrinkle and its application Elastic 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 Nano channels for fluidic application: protein precondensation Dry/wet adhesives for soft systems Wrinkled hard skin with focused ion beam Hard 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 morphologies Straight, herringbone, nested herringbone with multi-scale widths Artificial fabrication of nano-micro multi-scale surface morphologies

47 References [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) [2] M.-W. Moon, S. H. Lee, J.-Y. Sun, K. H. Oh, A. Vaziri, J. W. Hutchinson, Scripta materialia, 57 (2007) [3] S. Chung, J. H. Lee, M.-W. Moon, J. Han, R. D. Kamm, Advanced Materials ( ). [4] J Huang, M Juszkiewicz,W H. de Jeu, E Cerda,T Emrick, N Menon, T P. Russell, Science, 317(2007) pp [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. [7] E.P. Chan and A.J. Crosby, Adv. Mater. 18 (2006) [8] C. Harrison, C.M. Stafford, W. Zhang, A. Karim, Appl. Phys. Lett. 85 (2005) [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) [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) [14] T. Ohzonoa, M. Shimomuraa, Phys. Rev. E 73 (2006)

48 Acknowledgments Collaborators KIST - 이광렬박사, 이진우박사, Dr. Sk. Faruque Amhed SNU - 오규환교수, 선정윤, 이상훈, 허은규김호영교수, 차태곤, 서갑양교수, Yudi Rahmawan Harvard Prof. John W. Hutchinson Dr. Ashkan Vaziri MIT Prof. Kamm, Prof. Han, 정석박사, 이정훈박사 Funding from - 21st Century Frontier R&D Programs of Center for Nanostructured Materials Technology - Korea Research Foundation

49 Thanks!!! Please ask questions for further details!!!

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