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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics 1
Nanotribology, Nanomechanics and Materials Characterization Studies and Applications to
Bio/nanotechnology and Biomimetics
Prof. Bharat BhushanOhio Eminent Scholar and Howard D. Winbigler Professor
and Director [email protected]
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
© B. Bhushan
Micro/nanoscale studies
Techniques
Bio/nanotribology Bio/nanomechanics Biomimetics
Materials sci., biomedical eng., physics & physical chem.
NanoindentorMicrotriboapparatusAFM/STM
Materials/DeviceStudies
• Materials/coatings• SAM/PFPE/Ionic liquids• Biomolecular films• CNTs
• Micro/nanofabrication
Collaborations
• MEMS/NEMS• BioMEMS/NEMS• Superhydrophobic surfaces• Reversible adhesion• Beauty care products• Probe-based data storage• Aging Mech. of Li-Ion Batt.
Applications
Numerical modeling and simulation
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics 3
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Outline• Introduction
NanotribologyExamples of a magnetic storage device, MEMS/NEMS and BioMEMS/BioNEMS
• Measurement Techniques
• Results and ConclusionsSurface Imaging, Adhesion, Friction and Wear Adhesion, Friction and Wear of CNTsBioadhesion StudiesHierarchical Nanostructures for Superhydrophobicity, Self Cleaning and Low AdhesionConclusions
4
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Nanotribology• At most interfaces of technological relevance, contact occurs at
numerous asperities. It is of importance to investigate a singleasperity contact in the fundamental tribological studies.
• Nanotribological studies are neededTo develop fundamental understanding of interfacial phenomena on a small scaleTo study interfacial phenomena in micro- or nanostructures and performance of ultra-thin films, e.g., in magnetic storage and MEMS/NEMS components
Tip - based microscope allows simulation of a single asperity contact
Engineering Interface
Introduction
B. Bhushan, J. Israelachvili and U. Landman, Nature 374, 607 (1995); B. Bhushan, Handbook of Micro/Nanotribology, second ed., CRC Press, 1999;B. Bhushan, Introduction to Tribology, Wiley, NY, 2002; B. Bhushan, Nanotribology and Nanomechanics – An Introduction, Springer, 2005; B. Bhushan, Wear 259, 1507 (2005); B. Bhushan, Springer Handbook of Nanotechnology, second ed., Springer, 2007.
5
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Magnetic rigid–disk drive (Bhushan, 1996) MR type picoslider
Diamond like carbon overcoat3.5 nm thick
Al2O3-TiC
Liquid Lubricant 1- 2 nm
Diamondlike carbon overcoat 3-5 nm
Magnetic coating 25 –75 nmAl-Mg/10 μm Ni-P, Glass or
Glass - ceramic 0.78-1.3 mm
Thin–film disk
Example of a Magnetic Storage Device
B. Bhushan. Tribology and Mechanics of Magnetic Storage Devices, 2nd ed., Springer-Verlag, NY, 19966
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Microgear unit can be driven at speeds up to 250,000 RPM. Various sliding comp. are shown after wear test for 600k cycles at 1.8% RH (Tanner et al., 2000)
Microengine driven by electrostatically-actuatedcomb drive
Sandia Summit Technologies (www.mems.sandia.gov)
shuttle
springs
gears and pin joint
Stuck comb drive
Examples of MEMS/NEMS and BioMEMS/NEMS
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Microfabricated commercial MEMS components
8
B. Bhushan. Springer Handbook of Nanotechnology, second ed., Springer-Verlag, Heidelberg, 2007
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
The generating points of friction and wear due to interaction ofa biomolecular layer on a synthetic microdevice with tissue
(Bhushan et al., 2006)
9
SWNT biosensor
MWNT Sheet
Mechanical properties of nanotube ribbons, such as the elastic modulus and tensile strength, critically rely on the adhesion and friction between nanotubes.
The electrical resistance of the system is sensitive to the adsorption of molecules to the nanotube/electrode.Adhesion should be strong between adsorbents and SWNT.
Force applied at the free end of nanotube cantilever is detected as the imbalance of current flowing through the nanotube bearing supporting the nanotube cantilever.The deflection of nanotubecantilever involves inter-tube friction.
(Chen et al., 2004)
(Zhang et al., 2005)
(Roman et al., 2005)
CNT-based Nanostructures
Nanotube bioforce sensor
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Measurement Techniques
Atomic Force Microscope (AFM) andFriction force Microscope (FFM), 1985
B. Bhushan, J. Israelachvili and U. Landman, Nature 374, 607 (1995); B. Bhushan, Handbook of Micro/Nanotribology, second ed., CRC Press, 1999;B. Bhushan, Introduction to Tribology, Wiley, NY, 2002; B. Bhushan, Nanotribology and Nanomechanics – An Introduction, Springer, 2005;B. Bhushan, Springer Handbook of Nanotechnology, second ed., Springer, 2007.
Surface Force Apparatus (SFA),1968
Scanning Tunneling Microscope (STM), 1981
11
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Schematic of a small sample AFM/FFM
Schematic of a large sample AFM/FFM
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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
STM images of a solvent-deposited C60 film on gold coated mica
Results – Surface Imaging and Friction
B. Bhushan et al., J. Phys. D: Appl. Phys. 26, 1319 (1993)CNN Headlines News, 3/18-3/19/93, etc.
13
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
μ = 0.006
J. Ruan and B. Bhushan, J. Appl. Phys. 76, 8117 (1994); Y. Song and B. Bhushan, Phys. Rev. B 74, 165401 (2006)National Public Radio, 4/12/95; Business Week, 5/1/95 etc.
Topography and friction force maps for HOPG
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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Friction force map and line plots of friction force profiles for HOPG. Friction force changes discontinuously with sudden jumps. This leads to saw tooth pattern and it occurs due to atomic-scale stick-slip. Can use mechanical model proposed by Tomlinson in 1929.
Direction of motion of sample surface
AFM tip-cantilever
model
Samplesurface
Stick Slip
Periodic interaction potential
Slip event is a dissipative process
Equilibrium position before sliding begins
Atomic lattice constant, a
The tip needs to overcome the energy barrier in order to jump from a stable equilibrium on the surface into a neighboring position. The tip remains stuck until energy stored in the spring is high enough to overcome the energy barrier. 15
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Roughness, nano- and macroscale friction data of various samples
Coefficient of Friction
SampleRMS*(nm)
Nanoscale*with Si3N4
tip
Microscalewith Si3N4
ballSi(100) 0.14 0.06 0.47HOPG 0.09 0.006 0.1Natural
Diamond2.3 0.05 0.2
DLC film 0.14 0.03 0.19
*Scan area = 1 μm x 1 μm
Scale effect on friction
J. Ruan and B. Bhushan, ASME J. Tribol. 116, 389 (1994)B. Bhushan et al., ASME J. Tribol. 126, 583 (2004)
16
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Comparing the conditions of nanoscale and macroscale tests,there are at least four differences
•Contact size in FFM is small—particles are ejected readily
•Mechanical properties have size effect—properties on nanoscale are superior to the bulk properties
•Applied loads in FFM are low—elastic contact regime (little plowing)
•Small radius of tip results in lower friction
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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Schematic of experimental setupN. Tambe and B. Bhushan, J. Phys. D: Appl. Phys. 38, 764 (2005); Z. Tao and B. Bhushan, Rev. Sci. Instrum. 77, 103705 (2006)
Custom piezo stages for high velocity sliding
Ultrahigh velocity stage (upto 200 mm/s) High velocity stage (upto 10 mm/s)
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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
• Friction mechanisms vary with surfaces• At different velocity regime, different mechanisms dominate friction
N. S. Tambe and B. Bhushan, Nanotechnology 15, 1561 (2004); ibid, 16, 2309 (2005); J. Phys. D: Appl. Phys. 38, 764 (2005);Appl. Phys. Lett. 86, 061906, 2005; J. Vac. Sci. Technol. A 23, 830 (2005); Ultramicroscopy 105, 238 (2005); Z. Tao and B. Bhushan, Rev. Sci Instrum. 77, 103705 (2006); J. Vac. Sci. Technol. A 25 1267(2007)
Friction force on log scaleNormal load = 100 nN
60
40
20
0
Si (100)
Fric
tion
forc
e (n
N)
60
40
20
0
DLC
Meniscus force dominates
Atomic-scale stick slip dominates
Viscous shear dominates
Atomic-scale stick slip dominates
Phase transformation/ tip jump
Velocity (μm/s)100 102 104 106
Friction force on log scaleNormal load = 100 nN
60
40
20
0
Si (100)
Fric
tion
forc
e (n
N)
60
40
20
0
DLC
Meniscus force dominates
Atomic-scale stick slip dominates
Viscous shear dominates
Atomic-scale stick slip dominates
Phase transformation/ tip jump
Velocity (μm/s)100 102 104 106
Velocity (μm/s)100 102 104 106
100 101 102 103
Friction force on log scale (low velocity)
10
5
010
5
0
Fric
tion
forc
e (n
N)
Velocity (μm/s)
Si (100)
DLC
100 101 102 103
Friction force on log scale (low velocity)
10
5
010
5
0
Fric
tion
forc
e (n
N)
Velocity (μm/s)
Si (100)
DLC
Friction force on linear scale
Si (100)
DLC
0 105 2 × 105
Velocity (μm/s)
60
40
20
0
Fric
tion
forc
e (n
N)
60
40
20
0
Friction force on linear scale
Si (100)
DLC
0 105 2 × 105
Velocity (μm/s)0 105 2 × 105
Velocity (μm/s)
60
40
20
0
Fric
tion
forc
e (n
N)
60
40
20
0
Effect of velocity on friction force
19
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Contour map showing friction force dependence on normal load and sliding velocity.
N. S. Tambe and B. Bhushan, Appl. Phys. Lett. 86, 193102 (2005); Nature Mat. In Nanozone, Feb. 17 (2005)
Nanofriction maps
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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Nanowear map for DLC illustrating effect of sliding velocity and normal load.
Nanowear map
N. S. Tambe and B. Bhushan Scripta Mat. 52, 751 (2005); Tribol. Lett. 20, 83 (2005).
21
Experimental Schematic MWNT tip and SWNTs suspended on a micro-trench
Average diameter of suspended SWNT bridge is 1.43 nmThe diameter of the MWNT tip is about 100 nm.Method (1) works for flexible MWNT tip while method (2) is suitable for stiff MWNT tip
Adhesion and Friction between Individual Nanotubes
B. Bhushan, X. Ling, A. Jungen, C. Hierold, Phys. Rev. B, 2008
(1) Scan of MWNT tip in lateral direction across suspended SWNT bridge
(2) Ramp of MWNT tip in vertical direction against suspended SWNT bridge
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
(A) Nanotubes came into contact and formed a movable junction.By analyzing the dissipated power of the vibrating cantilever, the kinetic friction between nanotube is proportional to the attenuation of the cantilever amplitude during the initial contact of nanotube:
FF = 4 ± 1 pN(B) The junction slipped to the end of the MWNT tip with the
deformation of the tip.(C) The adhesive force between nanotubes forced the nanotubes to
deform more until they detached from each other.
Multiplying cantilever deflection at the point of detachment with cantilever spring constant gives:
FA = 0.7 ± 0.3 nN
The coefficient of kinetic friction is calculated from FF / FA :µ = 0.006 ± 0.003
Comparable to values reported on graphite on nanoscale.
Scan of MWNT tip in lateral direction across suspended SWNT bridge
Cantilever tapping amplitude
0
16 nm21 nm
Cantilever vertical deflection
-1.2 nm0.8 nm
2.4 µm
A B C
(A) (B) (C)
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics 23
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Bioadhesion Studies
• Study surface modification approaches - nanopatterning and chemical linker method to improve adhesion of biomolecules on silicon based surfaces.
B. Bhushan et al., Acta Biomaterialia 1, 327 (2005) ; ibid 2, 39 (2006); Lee et al., J. Vac. Sci. Technol. B 23, 1856 (2005) ; Tokachichu and Bhushan, IEEE Trans. Nanotech. 5, 228 (2006); Eteshola et al., J. Royal Soc. Interf. 5, 123(2008)
24
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
STA: StreptavidinAPTES:AminopropyltriethoxysilaneNHS: N-hydroxysuccinimidoBSA: Bovine serum albumin
Sample preparation
25
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Schematic representation of deposition of streptavidin (STA) by chemical linker method
26
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Adhesion measurements in PBS with functionalized tips
Patterned silica surface exhibits higher adhesion compared to unpatterned silica surface. Biotin coated surface exhibits even higher
adhesion. 27
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Biomimetics• Nature has gone through evolution over 3.8 billion years. It has evolved
objects with high performance using commonly found materials.• Biological inspired design or adaptation or derivation from nature is
referred to as biomimetics. It means mimicking biology or nature. Biomimetics is derived from a Greek word “biomimesis.” Other words used include bionics, biomimicry and biognosis.
• Biomimetics involves taking ideas from nature and implementing them in an application.
• Biological materials have hierarchical structure, made of commonly found materials.
• It is estimated that the 100 largest biomimetic products had generated $1.5 billion over 2005-08. The annual sales are expected to continue to increase dramatically.
28
M. Nosonovsky and B. Bhushan (2008), Multiscale Dissipative Mechanisms and Hierarchical Surfaces: Friction, Superhydrophobicity, and Biomimetics, Springer-Verlag, Heidelberg, Germany; B. Bhushan (2007), Springer Handbook of Nanotechnology, second ed., Springer-Verlag, Heidelberg, Germany; B. Bhushan, Phil. Trans. R. Soc. A (in press).
Lessons From Nature (Biomimetics)
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics 29
Montage of some examples from nature.
B. Bhushan, Phil. Trans. R. Soc. A (in press).
Montage of some examples from nature
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
SEM of Lotus leaf showing bump structure.
One of the crucial property in wet environments is non-wetting or superhydrophobicity and self cleaning. These surfaces are of interest in various applications, e.g., self cleaning windows, windshields, exterior paints for buildings, navigation-ships and utensils, roof tiles, textiles and reduction of drag in fluid flow, e. g. in micro/nanochannels. Also, superhydrophobic surface can be used for energy conservation and energy conversion such as in the development of a microscale capillary engine.
Reduction of wetting is also important in reducing meniscus formation, consequently reducing stiction.
Various natural surfaces, including various leaves, e. g. Lotus, are known to be superhydrophobic, due to high roughness and the presence of a wax coating (Neinhuis and Barthlott, 1997)
NY Times, 1/27/05; ABCNEWS.com, 1/26/05; Z. Burton and B. Bhushan, Ultramicroscopy 106, 709 (2006); B. Bhushan and Y. C. Jung, Nanotechnology 17, 2758 (2006); B. Bhushan and Y. C. Jung, J. Phys.: Condens. Matter 20, 225010 (2008)
Hiearchical Nanostructures for Superhydrophobicity, Self-cleaning and Low Adhesion
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Rolling off liquid droplet over superhydrophobic Lotus leaf with self cleaning ability
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Wenzel’s equation:
cos cosf oRθ θ=
Roughness optimization model for superhydrophobic and self cleaning surfaces
Droplet of liquid in contact with a smooth and rough surface
Effect of roughness on contact angle
M. Nosonovsky and B. Bhushan, Microsyst. Tech. 11, 535 (2005); Microelectronic Eng. 84, 387 (2007); Ultramicroscopy 107, 969 (2007); J. Phys.: Condens. Matter 20, 225009 (2008); US Patent pending (2005)
SL 0 LAcos cosfR f fθ θ= −
0 LA 0cos ( cos 1)f fR f Rθ θ= − +
fLA requirement for a hydrophilic surface to be hydrophobic
Cassie-Baxter equation:
Formation of the composite interface
Y. C. Jung and B. Bhushan, Nanotechnology 17, 4970 (2006); B. Bhushan and Y. C. Jung, J. Phys.: Condens. Matter 20, 225010 (2008); M. Nosonovsky and B. Bhushan, Microsyst. Tech. 12, 231 (2006); ibid, 273 (2006)
0LA 0
0
cos for 90
cos 1f
f
Rf
Rθ
θθ
≥ <+
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
recadv θθ −
)1cosθ(2)cosθ(cosθ1
θθ0
adv0rec0recadv +
−−≈−
f
LAf
RfR
http://lotus-shower.isunet.edu/the_lotus_effect.htm
Increase in fLA and reduction in Rf decrease
Increased droplet volume
Decreased droplet volume
α : Tilt angle
for high contact angle(θ 180°)
θadv : Advancing contact angle
θrec : Receding contact angle
θH = θadv - θrec
B. Bhushan and Y. C. Jung, Ultramicroscopy 107, 1033 (2007); J. Phys.: Condens. Matter 20, 225010 (2008); B. Bhushan, M. Nosonovsky, and Y. C. Jung, J. R. Soc. Interf. 4, 643 (2007); M. Nosonovsky and B. Bhushan, Microelectronic Eng. 84, 382 (2007); Nano Letters 7, 2633 (2007); Springer-Verlag, Heidelberg (2008) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
If θH is low, energy spent during movement of a droplet is small and a droplet can move easily at a small tilt angle
In fluid flow, another property of interest is contact angle hysteresis (θH)
• MaterialsSample
Poly(methyl methacrylate) (PMMA) (hydrophilic) for nanopatternsand micropatterns
Hydrophobic coating for PMMAPerfluorodecyltriethyoxysilane (PFDTES) (SAM)
Z. Burton and B. Bhushan, Nano Letters 5, 1607 (2005); Y. C. Jung and B. Bhushan, Nanotechnology 17, 4970 (2006); B. Bhushan and Y. C. Jung, J. Phys.: Condens. Matter 20, 225010 (2008);
Low aspect ratio (LAR) – 1:1 height to diameter
High aspect ratio (HAR) – 3:1 height to diameter Lotus patterned
Nanopatterns Micropatterns
Study the effect of nano- and microstructure on superhydrophobicity
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Fabrication and characterization of nanopatterned polymers
Contact angle on micro-/nanopatterned polymers• Different surface structures: film, Lotus, LAR, HAR• Hydrophobic film, PFDTES, on PMMA and PS surface structures
• In hydrophilic surfaces, contact angle decreases with roughness and in hydrophobic surfaces, it increases.
• The measured contact angles of both nanopatterned samples are higher than the calculated values using Wenzel equation. It suggests that nanopatterns benefit from air pocket formation. Furthermore, pining at top of nanopatterns stabilizes the droplet.
LAR HAR Lotus
Rf 2.1 5.6 3.2
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Transition for Cassie-Baxter to Wenzel regime depends upon the roughness spacing and radius of droplet. It is of interest to understand the role of roughness and radius of the droplet.
Optical profiler surface height maps of patterned Si with PF3
• Different surface structures with flat-top cylindrical pillars:Diameter (5 µm) and height (10 µm) pillars with different pitch values
(7, 7.5, 10, 12.5, 25, 37.5, 45, 60, and 75 µm)
• MaterialsSample – Single-crystal silicon (Si)Hydrophobic coating – 1, 1, -2, 2, -tetrahydroperfluorodecyltrichlorosilane (PF3) (SAM)
B. Bhushan and Y. C. Jung, Ultramicroscopy 107, 1033 (2007); J. Phys.: Condens. Matter 20, 225010 (2008); B. Bhushan, M. Nosonovsky, and Y. C. Jung, J. R. Soc. Interf. 4, 643 (2007); Y. C. Jung, and B. Bhushan, Scripta Mater. 57, 1057 (2007); J. Microsc. 229, 127 (2008); Langmuir 24, 6262 (2008); M. Nosonovsky and B. Bhushan, Ultramicroscopy 107, 969 (2007); Nano Letters 7, 2633 (2007); J. Phys.: Condens. Matter 20, 225009 (2008); Mater. Sci. Eng.:R 58, 162 (2007) ; Langmuir 24, 1525 (2008)
Fabrication and characterization of micropatterned silicon
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Transition from Cassie-Baxter regime to Wenzel regime
Transition criteria for patterned surfaces
• Geometry (P and H) and radius R govern transition. A droplet with a large radius (R) w.r.to pitch (P) would be in Cassie-Baxter regime.
• The curvature of a droplet is governed by Laplace eq. which relates pressure inside the droplet to its curvature. The maximum droop of the droplet
If δ ≥ H
RD)P2(δ
2−≈
Y. C. Jung, and B. Bhushan, Scripta Mater.57, 1057(2007); Y. C. Jung, and B. Bhushan, J.Microsc. 229, 127 (2008); B. Bhushan and Y. C. Jung, J. Phys.: Condens. Matter 20, 225010 (2008)
Contact angle, hysteresis, and tilt angle on patterned Si surfaces with PF3
Droplet size = 1 mm in radius
• For the selected droplet, the transition occurs from Cassie-Baxter regime to Wenzel regime at higher pitch values for a given pillar height.
B. Bhushan, and Y. C. Jung, Ultramicroscopy 107, 1033 (2007); Y. C. Jung, and B. Bhushan, J. Microsc. 229, 127 (2008); B. Bhushan and Y. C. Jung, J. Phys.: Condens. Matter 20, 225010 (2008) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
• The critical radius of droplet for the transition increases with the pitch based on both the transition criterion and the experimental data.
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Structure of ideal hierarchical surface
• Based on the modeling and observations made on leaf surfaces, hierarchical surface is needed to develop composite interface with high stability.
• Proposed transition criteria can be used to calculate geometrical parameters for a given droplet radius. For example, , for a droplet on the order of 1 mm or larger, a value of H on the order of 30 μm, D on the order of 15 μm and P on the order of 130 μm is optimum.
• Nanoasperities should have a small pitch to handle nanodroplets, less than 1 mm down to few nm radius. The values of h on the order of 10 nm, d on the order of 100 nm can be easily fabricated.
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Fabrication and characterization of hierarchical surface
Fabrication of microstructure
• MicrostructureReplication of Lotus leaf and micropatterned silicon surface using an epoxy resin and then cover with the wax material
B. Bhushan et al., Soft Matter 4, 1799 (2008); Appl. Phys. Lett. 93, 093101 (2008); Ultramicroscopy (in press); Langmuir (in press); Koch et al., Soft Matter (in press)
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Fabrication of nanostructure and hierarchical structure
• NanostructureSelf assembly of the Lotus wax deposited by thermal evaporation
Expose to a solvent in vapor phase for the mobility of wax molecules• Hierarchical structure
Lotus and micropatterned epoxy replicas and covered with the tubules of Lotus wax
Recrystallization of wax tubules
B. Bhushan et al., Soft Matter 4, 1799 (2008); Appl. Phys. Lett. 93, 093101 (2008); Ultramicroscopy (in press); Langmuir (in press); Koch et al., Soft Matter (in press)
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Static contact angle, contact angle hysteresis, tilt angle and adhesive force on various structures
• Nano- and hierarchical structures with tubular wax led to high static contact angle of 167º and 173º and low hysteresis angle on the order of 6º and 1º.
• Compared to a Lotus leaf, hierarchical structure showed higher static contact angle and lower contact angle hysteresis.
B. Bhushan, Y. C. Jung, A. Niemietz, and K. Koch, Langmuir (in press)
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Self-cleaning efficiency of various surfaces
• As the impact pressure of the droplet is zero or low, most of particles on nanostructure were removed by water droplets, resulting from geometrical scale effects.
• As the impact pressure of the droplet is high, all particles which are sitting at the bottom of the cavities between the pillars on hierarchical structure were removed by the water droplets.
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Conclusions
• AFM/FFM has been developed as a versatile tool for fundamental studies in nanotribology, nanomechanics and material characterization.
• It has been successfully used for studies of surface imaging, adhesion, friction, scratching/wear, lubrication, measurement ofmechanical and electrical properties, and in-situ localized deformation studies.
• Examples of nano/biotechnology and biomimetics research are presented.
46
Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
Acknowledgements• Financial support has been provided by the Office of Naval
Research, National Science Foundation, the Nanotechnology Initiative of the National Institute of Standards and Technology in conjunction with Nanotribology Research Program, and industrial membership of NLBB.
• The self assembled monolayers (SAMs) were prepared by Dr. W. Eck and Prof. M. Grunze at University of Heidelberg, Germany, and Drs. P. Hoffmann and H. J. Mathieu of EPFL Lausanne, Switzerland.
• Some of the patterned samples were provided by Dr. E. Y. Yoon ofKIST Korea and Drs. P. Hoffmann and L. Barbieri of EPFL, Lausanne, Switzerland.
• The BioMEMS/BioNEMS studies were carried out in collaboration with Prof. S. C. Lee of OSU Medical School.
• Physik Instrumente provided high speed piezo stages.
• Last but not the least, contributions by my past and present students and visiting scientists is gratefully acknowledged.
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Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics
References• Bhushan, B., Israelachvili, J. N. and Landman, U. (1995), "Nanotribology: Friction,
Wear and Lubrication at the Atomic Scale,” Nature 374, 607-616.
• B. Bhushan (1999), Handbook of Micro/Nanotribology, second ed., CRC Press, Boca Raton, Florida.
• Bhushan, B. (2001), Modern Tribology Handbook, Vol. 1 & 2, CRC, Boca-Raton, Florida.
• Bhushan, B. (2002), Introduction to Tribology, Wiley, New York.
• Bhushan, B., Fuchs, H., et al. (2004, ’06, ’07, ’08, ‘09), Applied Scanning Probe Methods, Vol. 1-13, Springer-Verlag, Heidelberg, Germany.
• Bhushan, B. (2007), Springer Nanotechnology Handbook, second ed., Springer-Verlag, Heidelberg, Germany.
• Bhushan, B. (2008), Nanotribology and Nanomechanics – An Introduction, second ed., Springer-Verlag, Heidelberg, Germany.
• Bhushan, B. (2008), “Nanotribology, Nanomechanics and NanomaterialsCharacterization” Phil. Trans. R. Soc. A 366, 1351-1381.
• Bhushan, B. (2009), “Biomimetics – Lessons from Nature: An Overview”, Phil. Trans. R. Soc. A (in press).
http://mecheng.osu.edu/nlbb 48
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