Nanotribology of Human Hair and Conditioner and Skin ... · • Hair cellular structure...

Nanotribology of Human Hair and Conditioner and Skin Creamand Skin Cream

Using AFM and Nanoindentation

Prof. Bharat BhushanOhio Eminent Scholar and Howard D Winbigler ProfessorOhio Eminent Scholar and Howard D. Winbigler Professor

and Director [email protected]

Nanotribology Laboratory for Information Storage and MEMS/NEMS

© B. BhushanNanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics

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Micro/nanoscale studies

Bio/nanotribology Bio/nanomechanics Biomimetics

Materials sci biomedical eng physics & physical chem

Materials/DeviceStudies

• Materials/coatings

Techniques

Materials sci., biomedical eng., physics & physical chem.

NanoindentorMicrotriboapparatusAFM/STM

• SAM/PFPE/Ionic liquids• Biomolecular films• CNTs

• Micro/nanofabricationNanoindentorMicrotriboapparatusAFM/STM

Collaborations Applications

Numerical modeling and simulation

Collaborations

• MEMS/NEMS• BioMEMS/NEMS• Superhydrophobic surfaces• Reversible adhesion

Applications

• Reversible adhesion• Beauty care products• Probe-based data storage

Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics

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Laboratory Facilities5700 sq. ft. of lab space (T&H controlled; part lab – class 100 clean room)

Major Equipment• Scanning tunneling microscope & five Atomic force/Friction force

microscopesp• Noncontact optical profiler and stylus profiler• Microhardness and Nanohardness testers• High vacuum tribotest apparatus equipped with mass spectrometer and

Augerg• Microtriboapparatus for Micro/Nanoscale Devices• Pin-on-disk type continuous/Reciprocating sliding test apparatuses• Vapor and liquid deposition facilities for self-assembled monolayers and

liquid lubricationq• Scanning ellipsometer• Particle counters/Optical microscopes/Microbalance/Environmental

chambers• Micro/nanofabrication facilities for bio/nanotechnology and biomimetics gy

research• Access to various physical and chemical analyses facilities at OSU


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Director: Prof. Bharat BhushanSenior/Visiting Scientists2005- Dr. Manual L. B. Palacio, “Nanoindentation,” Ph. D. Materials Science and Eng.

2009- Dr. Hyungoo Lee, “AFM Nanotribology,” Ph.D. Mechanical Engineeringy g gy g g

2010- Usama Heiba, “Nanotribology of Contact Switches,” Ph.D. Mechanical Engineering

2010- Dr. Monalisa Mazumder, “AFM Characterization of Biologically Active Electrokinetically-Altered Fluids ” Ph D Chemical EngineeringFluids, Ph.D. Chemical Engineering

Ph.D. Students2006- Shrikant C. Nagpure, “Multiscale Characterization of Aging Phenomena in Li-Ion Batteries,”

Department of Mechanical Engineering

2010- Daniel R. Ebert, “Biomimetics,” Department of Mechanical Engineering

M.S. Student2009- Brian Dean, “Biomimetics,” Department of Mechanical Engineering2009 Brian Dean, Biomimetics, Department of Mechanical Engineering

2010- James Hunt, “Adaptive Optics for Microprojectors,” Department of Mechanical Engineering.

2010- Steven Englehaupt, “Tribology of Skin Cream,” Department of Mechanical Engineering.


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Sponsors

IndustrialCorning

RevalesioMicroMedMicroMedTechnova

Government SponsorsGovernment SponsorsNational Science FoundationNational Institute of Health

Institute for Materials ResearchEuropean Unionp

Instrumentation SupportVeeco Instruments


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Industrial Membership Fees

• Annual membership fee is an unrestricted annual grant to NLBB

• Three levels of membershipMember $ 25,000Advisory Member $ 50,000Senior Member $ 75 000Senior Member $ 75,000Corporate Member $100,000

• Members will have limited access to lab facilities AdvisoryMembers will have limited access to lab facilities. Advisory, senior and corporate members can initiate and guide research project.

• Contract research can also be initiated. The cost usually runs from $60 to $100 k per year.


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Sponsor Benefits

• Access to all laboratory facilities

• Initiate and guide a research project (Advisory Senior and• Initiate and guide a research project (Advisory, Senior and Corporate members)

• Receive all written reports before they are submitted for external p ypublication or are available for general distribution

• Attend Industry/University Technical Exchange meetings held once per yearonce per year

• May send one representative to any short courses offered by NLBB

• May place a visiting Industrial Fellow for any period


• List of students available for employment8

Ongoing Research Projects

Nanotribology and Nanomechanics• Influence of Water on the Interaction Between Graphite and Carbon Nanotubes• Nanotribological and Electrical Characterization of Ultrathin Wear-Resistance Ionic Liquid Films

Bio- & Nanotechnology• AFM Characterization of Biologically Active Electrokinetically-Altered Fluids• Nanolubrication of Sliding Components in Adaptive Optics Used in Microprojectors• Charging/Discharging in Capacitive RF-MEMS Switches Using an AFMg g g g p g• Morphology and Mechanical Properties of Block Copolymer Films for Bone Regeneration Applications (with

Prof. S. Schricker, College of Dentistry)


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Biomimetics• Lotus Effect: Roughness-Induced Superhydrophobic Surfaces• Mechanically Durable Superhydrophobic, Self-Cleaning, and Low-Drag Surfaces with Hierarchical Structure• Shark-Skin Inspired Structures for Low Drag• Gecko-Inspired Hierarchical Structures for Reversible Adhesion

Beauty Care Products• Adhesion, Friction, and Wear Characterization of Skin and Skin Cream Using Atomic Force Microscopy

Batteries Aging• Aging Mechanisms in Lithium-ion Batteries (with Profs. S. Babu, G. Rizzoni, and Y. Guezennec, College of

Eng.)

htt // h d / lbb/http://www.mecheng.osu.edu/nlbb/


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Nanotribology of Hair and Hair Conditioner


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Introduction• Hair is nanocomposite biological fiber• Composed of dead cells mostly keratin proteins (65-95%) and water Keratin proteins – are

Hair structure

Composed of dead cells, mostly keratin proteins (65 95%) and water. Keratin proteins are condensation polymers of amino acids (mostly cystine)

• Three main components: Cuticle, (Robbins, 1994; Smith and Swift, 2002)

cortex, and medulla• Cuticle appears like tiles on a roof, is

multi-layered and is important in protection of hair.


• Lipid layer (18-MEA) composes outermost surface of cuticle.

B. Bhushan, C. LaTorre, G. Wei, and N. Chen., “Structural, Nanomechanical, and Nanotribological Characterization of Human Hair and Skin using Atomic Force Microscopy and Nanoindentation” in Springer Handbook of Nanotechnology, 2nd Ed. (Springer-Verlag, 2007)

(Negri and Cornell, 1993)

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Why is tribology important to hair?Desired hair

featureTribological attributes

Smooth feel in wet Low friction between hair

y gy p

and dry environments

and skin in respective environment

Shaking and bouncing during

Low friction between hair fibers and groups of hairg g

daily activitiesg

Easy combing and styling

Low friction between hair and comb (plastic) and low adhesion. Note: more complex styles may require higher adhesion between fibers.

Shampoos clean the hair and scalp of oilsShampoos – clean the hair and scalp of oils

Conditioners (gel network of cationic surfactants, fatty alcohols, silicones, and water) – Repair hair damage and make the hair easier to comb; prevent flyaway; add feel, shine, softness

Nanoprobe Laboratory for Bio- & Nanotechnology and BiomimeticsC. LaTorre and B. Bhushan, Ultramicroscopy 105 115 (2005); J. Vac. Sci. Technol. A 23, 1034 (2005)

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MotivationMotivation, Objective and Approach

• Everyone wants healthy hair and skin• Top three hair care companies all have sales in several billion dollars• Past research has focused on

Physical properties on macroscaleMorph./Struct. characterization using SEM/TEM (tedious sample prep/vacuum)Tribological work (mainly friction) usually done only on macroscale

Objective and Approach• Hair cellular structure characterization using AFM

Various ethnic hair including effect of locationCross-section and longitudinal sections of human hair

• Nanomechanical Property Characterization using nanoindenterHardness Young’s modulus creep scratch resistance and in situHardness, Young s modulus, creep, scratch resistance, and in-situ deformation response

• Nanotribological characterization using AFM/FFM.Surface roughness, friction, and adhesion

– Directionality effects and scale effects on friction and adhesiony• Conditioner distribution studies

TR mode, force calibration mode, and adhesive force mapping• Surface potential studies

Triboelectric charge


Various ethnic hair – Caucasian, Asian, and African hairVirgin, damaged (chem. damaged – colored and permed; mech. damaged - combed) and treated (w/conditioner)

Experimental Techniques

Schematic of a small sample AFM/FFM

Schematic of a large sample AFM/FFM


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Three-sided pyramidal (natural) diamond tip

Square pyramidal silicon nitride tip

Square pyramidal Single-crystal silicon tip

Carbon nanotube tip


Various AFM tips 16

Optical micrographs of standard tip and microtips of different radii


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Various AFM operating modesExperimental Techniques


Tapping mode (constant amplitude) is used for roughness measurements. Contact mode is used for adhesion, friction and durability studies. Torsional resonance (TR) mode (constant load) is used to measure in-plane (lateral) heterogeneity (elastic and viscoelastic properties).18

NanoindenterNanoindenter

SEM imagingg gPhilips XL-30 ESEMHair sample sputtered with thin gold coating prior to SEM g g pmeasurements


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• In situ tensile measurements were conducted using a gcustom-built tensile stage that attaches to the AFM base and uses a linear stepper motor to load a sample in tension.


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Tribometer with an environmental chamberTribometer with an environmental chamber

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Contact angle of hair, human skin, and AFM tipContact angle affects wettability of hair; one also needs to know how care products affect contact angle

Sample Contact angle (o) Surface energy (N/m)

Dry Soaked

Contact angle affects wettability of hair; one also needs to know how care products affect contact angle. Contact angle needs to be simulated in our measurements.

Virgin Caucasian hairVirgin treatedChemically damagedChemically damaged, treated

103a

88a

70a

79a

98a

92a

70a

84a

0.028b

y g ,Mechanically DamagedAsianAfrican

95a

92a

80a

Human skin - forehead- forearm

- finger

55c

88c

84d

74d

104 ( f

0.043c

0.038c

0.029d

0.024d

0 027104e (after soap washing)58e (before soap washing)

0.027e

Si N film 48f


Si3N4 film 48f

Si tip 51g

a Lodge and Bhushan (2006), measured using Wilhelmy balance method; b LaTorre et al. (2006); c Lerebour et al. (2000); d Schott (1971)e Ginn et al. (1968); f Tao and Bhushan (2006; JOT); gTao and Bhushan (2006; JPhys)

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Various ethnic hair using SEM

Hair Cellular Structure CharacterizationVarious ethnic hair using SEM


G. Wei, B. Bhushan, and P. M. Torgerson, Ultramicroscopy 105, 248 (2005) 23

Hair cross section

Asian hair seems to be the thickest (about 80 to 100

thi k l d)μm thick, nearly round), followed by African hair (about 50 to 100 μm thick, significantly elliptical) and s g ca y e p ca ) a dCaucasian hair (about 50 to 80 μm thick, elliptical).

Effect of locationEffect of location

Nanoprobe Laboratory for Bio- & Nanotechnology and BiomimeticsG. Wei, B. Bhushan, and P. M. Torgerson, Ultramicroscopy 105, 248 (2005).

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Cross section of virgin Caucasian hair

The cortex region, the cuticle region (5 layers of cuticle cells, ~2 μm ) and epoxy resin region are easily identified.

Several layers (typically 5 to 10) of cuticle cells (200 nm to 500 nm thick and visible length of 5 to 10 microns) and various sublamellar structure of the cuticle are

Nanoprobe Laboratory for Bio- & Nanotechnology and BiomimeticsN. Chen and B. Bhushan, J. Micros. 220, 96 (2005).

length of 5 to 10 microns) and various sublamellar structure of the cuticle are observed. Cortex region shows very fine circular structure of size about 50 nm, which represents the transverse face of the macrofibril and matrix.

Virgin Caucasian hair surface (near root and near tip)g ( p)

Intact cuticle edge

Lots of damages l th ti lalong the cuticle

edges

Parts of the cuticle outer sublamellar layers were removed and underneath


Parts of the cuticle outer sublamellar layers were removed and underneath layers (the A-layer, the endocuticle, the inner layer) are exposed.

N. Chen and B. Bhushan, J. Micros. 220, 96 (2005).26

Damage process of hair surfaceg p

As damages occur due to natural weathering or mechanical damage, parts of the cuticle outer sublamellar layers wear off and underneath layers will be exposed. Further damage will cause entire piece of cuticle to be broken off and the ghost which d li t th i i l b d f th ti l d i


delineate the original boundary of the cuticle edge is seen.

N. Chen and B. Bhushan, J. Micros. 220, 96 (2005).27

Summary

• Various sublamellar cellular structures of cuticle are easily observed using TR mode technique because of their distinct

Summary

observed using TR mode technique because of their distinct stiffness and viscoelastic properties.

• Surfaces of virgin hair near hair root end show little damage and intact smooth cuticle edges; damages occur near tip end of hair surfaces because of natural weathering andend of hair surfaces because of natural weathering and mechanical damage, exposing various sublamellar cuticle layers. Other features, such as the cuticle ghost edges and the epicuticle, are seen.


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Nanomechanical Property Characterization

Hardness (GPa) Elastic modulus (GPa) Cuticlea Cortexb Medullab Cuticlea Cortexb Medullab

Table Summary of hardness and elastic modulus of human hair.

Caucasian 0.32 ± 0.04 0.27 ± 0.02 ~ 0.19 6.0 ± 0.4 6.5 ± 0.5 ~ 5.5 Asian 0.39 ± 0.06 0.30 ± 0.02 ~ 0.18 7.5 ± 0.8 6.7 ± 0.3 ~ 5.8

African 0.24 ± 0.05 0.23 ± 0.06 ~ 0.16 4.8 ± 0.6 5.8 ± 0.7 ~ 5.0

a Obtained from the hair surface at normal load of 1 0 mNa. Obtained from the hair surface at normal load of 1.0 mNb. Obtained from the hair cross section at normal load of 1.0 mN

The Caucasian, Asian and African hair have different nanomechanical properties. It appears that Asian hair has the highest hardness, followed by Caucasian and African hair.


G. Wei, B. Bhushan, and P. Torgerson, Ultramicroscopy 105, 248 (2005).

Scratch resistanceScratch resistance

Nanoprobe Laboratory for Bio- & Nanotechnology and BiomimeticsG. Wei and B. Bhushan, Ultramicroscopy 106, 742 (2006)

Response of cuticle to tensionp

Most significant effect of tension –cuticle lift off due to extensibility differences

• Occurs at 20% strain• Endocuticle and cell membrane –

weak extensible ; exocuticleweak, extensible ; exocuticle, epicuticle – cross linked, rigid

• Difference in extensibility - interlayer shear forces20% strain failure in endocuticle and• 20% strain – failure in endocuticle and delamination - Outer cuticle lifts off

Nanoprobe laboratory for Bio- &Nanotechnology and Biomimetics

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Damage type Damaged hair - lift off + disappearance of ti l dDamage type cuticle edges

• Spongy Scales – remains of cuticle cells split upto endocuticle

Nanoprobe laboratory for Bio- &Nanotechnology and Biomimetics

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p gy p p• Damaged hair – weakened cuticles• Outer cuticle fractures, and inner layers show up, mechanically damaged –

early fracture (10%) because part of cuticle removed

Summary• The hardness and elastic modulus of hair decreased going from the

surface to the core. The cystine content variations in cuticle substructures and cortex were proposed to be responsible for the

y

p p presult.

• The Caucasian, Asian and African hair have different nanomechanical properties. It appears that Asian hair has the highest hardness,properties. It appears that Asian hair has the highest hardness, followed by Caucasian and African hair.

• Hair exhibits viscoelastic properties.• Hair scratches and gets damaged at high loads ess strainHair scratches and gets damaged at high loads. ess strain

• Tensile stress causes lifting of outer cuticle at 20% strain in dry hair, due to interlayer shear forces and separation between inner and outer cuticle layersouter cuticle layers.

• Chemical damage and mechanical damage cause weakening of outer cuticle. Lift off and fracture of outer cuticle. Fracture at 10% strain in mechanical damaged hair 20% in chemically damaged hair.


g y g• Conditioner - no observable effect on the tensile response.

Conditioner coats cuticle and improves tribological properties – no chemical/physical alteration. (data not shown)

Roughness and Friction

Nanotribological Characterization

Roughness and Friction Surface roughness and friction force maps of virgin and chemo-mechanically damaged hair

• Virgin hair: Intact cuticle, low friction

• Damaged hair: Severe cuticle wear, high friction


C. LaTorre and B. Bhushan, Ultramicroscopy 105, 115 (2005).

• True for all ethnicities34

Surface roughness and friction force maps of virgin and virgin treated (commercial conditioner) hair

• Virgin treated hair: accumulation of conditioner near cuticle edge

• High friction contrast due to meniscus contributions


• True for all ethnicitiesC. LaTorre and B. Bhushan, Ultramicroscopy 105, 115 (2005).

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Effect of cycling with stiff Si AFM tip (durability study)Effect of cycling with stiff Si AFM tip (durability study)

• Simulation of wear by loose ti l (i d)particles (i.e. sand)

• Friction for virgin hair increases (lipid layer worn away)

• Virgin treated hair shows no increase of friction (protectiveincrease of friction (protective covering)

• Chemically damaged hair friction was high and stayedfriction was high and stayed about the same


C. LaTorre and B. Bhushan, J. Vac. Sci. Technol. A 23, 1034 (2005)

Summary

• Nanotribological characterization has been conducted on human hair as a function of ethnicity, damage, a variety of

Summary

y, g , ytreatments, and environment.

• Friction force maps are excellent techniques for observingFriction force maps are excellent techniques for observing the effects of damage and conditioner treatment.


Conditioner treated damaged hair surface

Conditioner Distribution Studiesg

High TR phase contrast near cuticle edges--- unevenly distributed

diti lconditioner layer

No discriminated features due to a surface layer of conditioner


conditioner

N. Chen and B. Bhushan, J. Micros. 220, 96 (2005).

Conditioner film thickness estimation


B. Bhushan and G.S. Blackman, ASME J. Tribol. 113, 452 (1991); N. Chen and B. Bhushan, J. Micros. 221, 203 (2006); R. Lodge and B. Bhushan, J. Vac. Sci. Technol. A 24, 1258 (2006)

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Film thickness and adhesive force mappingpp g


N. Chen and B. Bhushan, J. Micros. 221, 203 (2006)R. Lodge and B. Bhushan, J. Vac. Sci. Technol. A 24, 1258 (2006)

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The negative charge of the hair is attracted to the positively h d diti l l ( ti i f t t ) hi hcharged conditioner molecules (cationic surfactants) which

results in conditioner deposition on the hair. It is even more true for damaged hair, since the damaging processes result in hair even more negatively charged.


g y g

C. LaTorre, B. Bhushan, et al., J. Cosmetic Sci. 57, 37 (2006)41

S

• Conditioner unevenly distributes on damaged treated hair surface and thicker conditioner films

Summary

treated hair surface and thicker conditioner films are found near the cuticle edges.

• The mechanisms behind conditioner deposition pand its effects on friction and adhesion have been determined to rely heavily on hair hydrophobicity charge damage levelhydrophobicity, charge, damage level, conditioner composition, and meniscus and shear effects.

• Amino silicones seem to attach to hair and give low friction (Data not shown)


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Surface Potential Studies

Objective• To measure local surface charge buildup on variety of hairs by Kelvin probe

microscopy

Objective

• Investigate effect of damage, conditioner treatments, and humidity

• Hair rubbed with latex finger cot 5 passes

Triboelectric charging• Hair rubbed with latex finger cot, 5 passes• Potential measured before and after rubbing with SCM-PIT tip


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• The charge on hair can dissipate rapidly The natural

Triboelectric charging

dissipate rapidly. The natural lipid layer on virgin hair surface and conditioner treatment increase mobility of surface charges dissipating trapped charges and reduce amount of charge accumulated.Chemically damaged hair with• Chemically damaged hair with no lipid layer increases amount of charge accumulated.

Nanoprobe Laboratory for Bio- & Nanotechnology and BiomimeticsR. Lodge and B. Bhushan, J. Colloid Interface Sci. 310, 321 (2007).

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Overall Summary

• Human hair is a nano-composite biological fiber. A lipid layer covers the outermost surface of cuticle which gets removedremoved.

• For a good dry and wet feel and combing with ease and itho t entanglement the hair s rface sho ld e hibitwithout entanglement, the hair surface should exhibit

low friction and adhesion. Mechanical and chemical damage needs to be minimized. A conditioner with lubricating ingredients is used to achieve theselubricating ingredients is used to achieve these properties.

• Nanoscale characterization of cellular structure and• Nanoscale characterization of cellular structure and mechanical properties as well as morphological, friction, adhesion and wear properties is essential, and has been successfully carried out using an AFM and nanoindenter.


successfully carried out using an AFM and nanoindenter.

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References• B Bhushan and C LaTorre “Nanotribological Characterization of Human Hair and Skin Using Atomic Force Microscopy (AFM) ” Applied Scanning Probe• B. Bhushan and C. LaTorre, Nanotribological Characterization of Human Hair and Skin Using Atomic Force Microscopy (AFM), Applied Scanning Probe

Methods IV – Industrial Applications, edited by B. Bhushan and H. Fuchs, Springer-Verlag, Heidelberg, Germany, 2006, pp. 35-103. B. Bhushan, C. LaTorre, G. Wei, and N. H. Chen, “Structural, Nanomechanical, and Nanotribological Characterization of Human Hair and Skin using Atomic Force Microscopy and Nanoindentation” in Springer Handbook of Nanotechnology, 2nd Ed. (Springer-Verlag 2007).

• B. Bhushan, G. Wei, and P. Haddad, “Friction and Wear Studies of Human Hair and Skin,” Wear 259, 1012-1021 (2005).

• N. Chen and B. Bhushan, “Morphological, Nanomechanical and Cellular Structural Characterization of Human Hair and Conditioner Distribution Using Torsional Resonance Mode in an AFM ” J Micros 220 96-112 (2005); A figure on the cover page of Part 2 Nov 2005Torsional Resonance Mode in an AFM, J. Micros. 220, 96-112 (2005); A figure on the cover page of Part 2, Nov. 2005.

• C. LaTorre and B. Bhushan, “Nanotribological Characterization of Human Hair and Skin Using Atomic Force Microscopy,” Ultramicroscopy 105, 155-175 (2005).

• C. LaTorre and B. Bhushan, “Nanotribological Effects of Hair Care Products and Environment on Human Hair using Atomic Force Microscopy,” J. Vac. Sci. Technol. A 23, 1034-1045 (2005).

• G. Wei, B. Bhushan, and P. M. Torgerson, “Nanomechanical Characterization of Human Hair Using Nanoindentation and SEM,” Ultramicroscopy 105, 248-266 (2005).

• G. Wei and B. Bhushan, “Nanotribological and Nanomechanical Characterization of Human Hair Using a Nanoscratch Technique,” Ultramicroscopy 106, 742-754 (2006).

• B. Bhushan and N. Chen, “AFM Studies of Environmental Effects on Nanomechanical Properties and Cellular Structure of Human Hair,” Ultramicroscopy106 755-764 (2006).

• N Chen and B Bhushan “Atomic Force Microscopy Studies of Conditioner Thickness Distribution and Binding Interactions on the Hair Surface ” J Micros• N. Chen and B. Bhushan, Atomic Force Microscopy Studies of Conditioner Thickness Distribution and Binding Interactions on the Hair Surface, J. Micros221, 203-215 (2006).

• C. LaTorre and B. Bhushan “Investigation of Scale Effects and Directionality Dependence on Adhesion and Friction of Human Hair Using AFM and Macroscale Friction Test Apparatus,” Ultramicroscopy 106, 720-734 (2006).

• C. LaTorre, B. Bhushan, J. Z. Yang, and P. M. Torgerson, “Nanotribological Effects of Silicone Type, Silicone Deposition Level, and Surfactant Type on Human Hair Using Atomic Force Microscopy,” J. Cosmetic Sci. 57, 37-56 (2006).

• R. A. Lodge and B. Bhushan, “Surface Characterization of Human Hair Using Tapping Mode Atomic Force Microscopy and Measurement of Conditioner Thickness Distribution,” J. of Vac. Sci. Technol. A 24, 1258 – 1269 (2006).

• R. A. Lodge and B. Bhushan, “Wetting Properties of Human Hair by Means of Dynamic Contact Angle Measurement,” J. Appl. Poly. Sci. 102, 5255-5265 (2006).

• R. A. Lodge and B. Bhushan, “Surface Potential Measurement of Human Hair Using Kelvin Probe Microscopy,” J. Vac. Sci. Technol. A 25, 893-902 (2007)

• R A Lodge and B Bhushan “Effect of Physical Wear and Triboelectric Interaction on Surface Charges Measured by Kelvin Probe Microscopy ” J Colloid


• R. A. Lodge and B. Bhushan, Effect of Physical Wear and Triboelectric Interaction on Surface Charges Measured by Kelvin Probe Microscopy, J. Colloid and Interface Science 310, 321-330 (2007).

• I. P. Seshadri and B. Bhushan, “In-situ Tensile Deformation Characterization of Human Hair with Atomic Force Microscopy,” submitted for publication.

http://mecheng.osu.edu/nlbb/

References

• B. Bhushan and C. LaTorre, “Structural, Nanomechanical, and NanotribologicalCharacterization of Human Hair and Skin using Atomic Force Microscopy and Nanoindentation” in Springer Handbook of Nanotechnology, 3rd Ed., pp. 1055-1170, S i V l H id lb G 2010Springer-Verlag , Heidelberg, Germany, 2010.

• B. Bhushan, “Nanoscale Characterization of Human Hair and Hair Conditioners”, Progress Mat. Sci. 53, 585-710 (2008).

T W d Bh h B “Adh i f i ti d h t i ti f ki d ki• Tang W. and Bhushan B., “Adhesion, friction and wear characterization of skin and skin cream using atomic force microscope,” Colloids Surf. B: Biointerfaces 76, 1-15 (2010).

• Tang W., Bhushan B., and Ge S., “Friction, adhesion, and durability and influence of humidity on adhesion and surface charging of skin and various skin creams using atomic f i ” J Mi 239 99 106 (2010)force microscopy,” J. Microscopy 239, 99-106 (2010)

• Tang W., Bhushan B., and Ge S., “Triboelectrification studies of skin and skin cream using Kelvin probe microscopy,” J. Vac. Sci. Technol. A 28, 1018-1028 (2010).

• Bhushan B. and Tang W., and Ge S., “Nanomechanical characterization of skin and skin ” J Mi Icream,” J. Microscopy, In press.

• Tang W. and Bhushan B., ““Surface, Tribological and Mechanical Characterization of Synthetic Skins for Cosmetic Science,” submitted.

http://www.mecheng.osu.edu/nlbb/

Nanotribology of Human Hair and Conditioner and Skin ... · • Hair cellular structure...

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