Nanoscale Engineering of Biointerfaces v

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Nanoscale Engineering of Biointerfaces via Parylene Coatings – paper presented at ICMCTF 2011. Abstract \"Anisotropic textured surfaces is generated in the same way in both the plant and animal kingdoms, using dual micro/nanoscale features to tune roughness and surface energy on structures as diverse as plant leaves, animal fur, and bird feathers. For example, a closer look at complex structures in water walking arthropods and lizard toe ... Shared on http://www.vacuumcoating.info

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Nanoscale Engineering of Biointerfaces via Directional Films 300 (a) Parallel 13 1. e: p +- Lateral 03 0. 250 200 150 100 50 0 0 50 100 o Sl o Sl 9 .8 :0 pe +- 03 0. Directional Wetting Sliding Against Columns Sliding With Columns 150 200 250 300 Normal Load (uN) Directional Friction Directional Transport Melik C. Demirel, PhD Associate Professor of Engineering Science and Mechanics, Materials Research Institute Pennsylvania State University April 29 th 2011 1

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Two-modes of Weight Support J.bush, advances in insect physiology vol. 34, pg 117 2

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Water walking arthropods maintain a Cassie State J.bush, advances in insect physiology vol. 34, pg 117 3

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Directional Nanofilms in Nature Water-walking insects, Arthropods J.bush, advances in insect physiology vol. 34, pg 117 Water Strider 4

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How can we synthesize directional nanofilms? Materials Synthesis  Top-down techniques  Bottom-up techniques Theory/Applications  Coatings for fluidic / Lateral propulsion  Jet impact & Capillary tube diode :  Directional folding of thin sheets  Directional Friction/Cell Adhesion 5

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We have shown… 300 (a) Parallel 3 .1 :1 pe o +- Lateral 03 0. 250 200 150 100 50 0 0 50 100 Sl DIRECTIONAL FRICTION 03 0. o Sl 89 0. e: p +- Sliding Against Columns Sliding With Columns 150 200 250 300 So, E, et al, J. of Physics-D, 2010 Normal Load (uN) DIRECTIONAL WETTING Cetinkaya, et. al ., Langmuir 2007 , 46 , 640. DIRECTIONAL TRANSPORT Malvadkar et al, Nature Materials, Vol. 9 (12), pg, 1023-1028, 2010

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We have shown… DIRECTIONAL CELL ADHESION Christofis et al , 2011, submitted DIRECTIONAL ORIGAMI Sekeroglu et al , 2011, submitted

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Bottom-up Method R 10  m R Di-R-[2.2]- p -cyclophane  R R CH 2  H C 2 [ H C 2 CH 2  ] Electron Microscopy (cross section) of PPX nanofilm R ( R  Flux ) n Poly(R- p -xylylene (PPX) nPPX Ballistic Monte Carlo Simulation of polymer film growth  Substrate  Cetinkaya, et. al ., J. Polym. Sci. B: Polym. Phys. 2008 , 46 , 640.

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Top-Down Technique Monomer Flux Polymerization d AAO Etch AAO roller PI PS roller 9

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Theory/Applications Materials Synthesis  Top-down techniques  Bottom-up techniques Theory/Applications  Coatings for fluidic / Lateral propulsion  Jet impact & Capillary tube diode :  Directional folding of thin sheets  Directional Friction/Cell Adhesion 10

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Coatings for fluidic / Lateral propulsion Demirel et al., Vol.9, iss, 12, Nature Materials, 2010 11

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Drop Volume 45 anisotropic pinning anisotropic release isotropic "+" isotropic "-" Drop 40 35 30 25 20 15 30 Pinning Direction 45 60 75 90 Tilt Angle,  Release Position Demirel et al., Nature Materials, 2010

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Ratchet Theory COLUMN SPACING COLUMN HYDROPHOBICTY 1.6 COLUMN TILT C 0 s l (a) q a = 95 , q r = 75 ,  = 55 ° C 0 q a 0 q r 0 C 0 1.4 1.2 1.0 40 50 60 70 80 90  (b)  = 55 , s = 0.80, l = 0.85 (c) q a = 95 , q r = 75 , s = 0.80, l = 0.85 Ratio of retention forces in pinning and release directions, C 0 , as a function of (a) nanorod spacing l , s ,(b) intrinsic contact angles q r 0 , q a 0 , (c) nanorod inclinaton . C 0 varies smoothly except for inclination angle, where the pinning and release directions reverse at critical values of the inclination, in particular, at the intrinsic receding contact angle.

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Anisotropic Jump Release Position Pinning Direction

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Capillary tube diode Demirel, Advanced Functional Materials, invited review, 2011 15

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Capillary tube diode substrate nanorod g air g 12 droplet meniscus (Adhesive Position) (Release Position) ~ N p gd , where N is the number of columns per unit area (40 million mm -2 ), g is the surface tension of water (72 dyne cm -1 ), and d is the column diameter (~150 nm) For our PPX film, the resulting net surface tension force is immense (~1 N mm -2 ). Since N is proportional to 1/ d 2 , the load-bearing capacity is inversely proportional to rod diameter.

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1-Dimensional Mechanical Anisotropy Lateral Position (um) -4 0 -3 -2 -1 0 1 2 3 4 50 100 Depth Sliding Direction 150 200 Against columns 250 300 With columns Test 118, 100 uN load, 0-degree orientation Depth 0° 180° Parallel We have demonstrated directional mechanical response Lateral Position (um) -4 0 -3 -2 -1 0 1 2 3 4 50 100 Sliding Direction 150 200 250 300 Test 128, 100 uN load, 90-degree orientation So, E, et al, J. of Physics-D, 2010 17

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1-Dimensional Mechanical Anisotropy 0° 180° Parallel 90° Perpendicular So, E, et al, J. of Physics-D, 2010 18

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1-Dimensional Mechanical Anisotropy 300 Lateral 0° 180° (a) Parallel 1 e: .1 3 0 +- .0 3 250 200 150 100 50 0 0 300 Sl op Sl o : pe 0. 89 +- 0. 03 Parallel Sliding Against Columns Sliding With Columns 50 100 150 200 250 300 Normal Load (uN) (b) Perpendicular 9 0. 99 + . -0 00 2 Lateral 90° 250 200 150 100 50 0 0 50 100 150 Sl op 1 e: .0 0 +- .0 1 pe : o Sl 2 Perpendicular Sliding Right Sliding Left 200 250 300 Normal Load (uN) 19

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1-Dimensional Mechanical Anisotropy Beam Equation Hooke’s Law  L F = E A L Solution  2   2 u   EI =   x 2   x 2  Solution 64 H 3 d b =  F x p Ed 4 3 d c = 4 H  F y p Ed 2 ? c ? b H • • Variations in total penetration depth may be more strongly correlated to film density, modulus Model does not include density, inter-column contact or friction 4 H Depth = d b cos(  ) + d c sin(  ) = p Ed 2  16 H 2   ) +  F y sin(  )  F cos(  2  x  3 d  20 Sliding perpendicular to film results in no hysteresis, predicted depths between

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ROADMAP of CREATING DIRECTIONAL NANOFILMS Timeline Rigid Structures Stimuli Responsive Structures Self Adapting Structures 10  m 1  m 5  m e.g. PPX, PPV e.g. Hydrogel, PNIPA, Shape Memory Polymers e.g. Peptide fibers 21

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Directional Films in Nature J.bush, advances in insect physiology vol. 34, pg 117 How does the water strider leg its eggs? …..It secretes a wax to overcome surface tension (Burst Release) 22

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Nanofilms that can Burst Release sample Demirel et.al., Soft Matter, 2010

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Stimuli Responsive Nanofilms Demirel et.al., Soft Matter, 2010

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Burst Release Mechanism of Coaxial Nanofilm Ince et.al., Soft Matter, 2011

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CONCLUSION Directional polymeric nanofilms offer the possibility of fabricating surfaces exhibiting tunable directional physical properties (i.e. folding, wetting, friction, etc..) by systematically varying and controlling the chemistry, morphology, and topology at the same time. 26

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Personnel and Funding WEB: http://www.personal.psu.edu/mcd18 Personnel Funding MRSEC Prof. Melik Demirel Lab (Penn State University): • Post-doctoral Fellows: Dr Gokhan Demirel, Dr. Hui Wang, • Graduate Students: Ping Kao, Eric So, Niranjan Malvadkar, Stephen Koytek, Mike Anderson, Koray Sekeroglu, Miguel Santiago ICAM • Undergraduates: Sean Stokes, Jessie Liang Collaborators: • John Bush (MIT): Fluid Mechanics • David Allara (Penn State): Surface Chemistry • Arthur Lesk (Penn State): Molecular Biology • Walter Dressick (NRL): Metallization • Matt Hancock (Harvard): Wetting Theory • Karen Gleason (MIT): Chemical Vapor Deposition 27