The University of Manchester Research

Biophysics of Curly Hair

Link to publication record in Manchester Research Explorer

Citation for published version (APA):Wortmann, F., & Wortmann, G. (2016). Biophysics of Curly Hair: Why is hair curly, wavy, or straight?.

Citing this paperPlease note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscriptor Proof version this may differ from the final Published version. If citing, it is advised that you check and use thepublisher's definitive version.

General rightsCopyright and moral rights for the publications made accessible in the Research Explorer are retained by theauthors and/or other copyright owners and it is a condition of accessing publications that users recognise andabide by the legal requirements associated with these rights.

Takedown policyIf you believe that this document breaches copyright please refer to the University of Manchester’s TakedownProcedures [http://man.ac.uk/04Y6Bo] or contact uml.scholarlycommunications@manchester.ac.uk providingrelevant details, so we can investigate your claim.

Download date:07. Aug. 2019

1

1

Biophysics of Curly Hair

Why is hair curly, wavy or straight?

Franz J. Wortmann, Gabriele Wortmann

School of Materials, University of Manchester, UK

2nd Mancunian Skin Club Annual International Workshop

14-15 April 2016, Manchester, UK

Franz J.Wortmann

Hair formation

Cell death

Spatial separation of celltypes.

Cell DifferentiationSynthesis & self-assemblyof specific proteins

Primary morphological components

2

Franz-J.Wortmann

BC Powell & GE Rogers in ‘Formation and Structure of Human Hair’, P Jollès, H Zahn, H Hoecker (eds), Birkhaeuser 1997, p.59-148

Biomaterial

Tissue

Physics & Engineering

Life Sciences

http://naturalnigerian.com/2012/03/hair-101-the-scalp-get-this-right-and-your-hair-will-grow/

2

Keratin Material : General Morphology of a Fiber

3Franz J. Wortmann

Basic, ethnic hair types

4

Franz-J.Wortmann

straight wavy curly

3

Crimp & fibre morphology in fine wool: Early investigations

Other geometries of cell separation lead toless pronounced or no crimp for other typesof wool.

Cell fractions change with fibre diameter:More ortho-, less clear separation – lesscrimp (Orwin & Woods, 1980)

Hypothesis: The side-by-sidestructure leads to the induction offibre crimp in Merino wool.

o-cortex on the outside

p-cortex on the inside

5Franz J.Wortmann

Horio & Kondo, 1953Mercer, 1954

Cortical cell distribution in straight & curled Japanese hair

Swift, 1997Kajiura et al, 2006Nagase et al, 2008

Orientation of IFs

Cell cross-section

para- ortho-type

Bryson et al. observed basically four types of cortical cells:

A: ortho-type – convex sideB: ortho/meso-typeC: para-type – concave sideD: minor component

6

Franz-J.Wortmann

Biomechanically, the side-by-side arrangementof o-type & p-type cells will upon keratinisationinduce fibre crimp (Munro & Carnaby, 1999)

4

Wool & hair: Cortex compositions

Thermal analysis (DSC) shows distinct differences forthe thermal stability of helical IF proteins in ortho-and para-type cells, leading to unsymmetricalendotherms.

The differences between denaturation temperaturesare distinct for wool and more subtle for human hairs.

Cortical cell fractions are very similar for differenthair types and size-wise in line with expectations forcoarse wool.

7Franz J.Wortmann

Hair Type ortho I, % ortho II , % para, %

Merino wool 12 56 32

African 11 68 21

Asian 9 60 31

European 10 64 26

This support the hypothesis, that curl is onlyrelated to the lateral segregation of cell typeswith different types of IF orientation.

Wool

Asian Hair

Quadflieg & Wortmann, 2011

IF denaturation & hair self-straightening

Due to the pronounced correlation between straightening ef fect and helix-content, themechanism of self-straightening is identified as the alkali-induced denaturation of α-helical segments in the IFs.

This in turn confirms the role of IFs and their orientation fo r maintaining macroscopichair shape.

http://escovaprogress.com/store/keratin-relaxer/gold-black-definitive-liss/

8

Franz-J.Wortmann

5

The role of fibre ellipticity for curl formation

9

Franz-J.Wortmann

Asian Hair European Hair African Hair

It is intuitively clear that for equal cross-sectional area an elliptical fibre will be easierto bend (across its short axis, b) than theequivalent circular fibre.

As a consequence elliptical fibres canform tight curls with only acomparatively low degree of stress-imbalance upon keratinization.

Round fibres for the same pre-conditionwould just form slight waves.

B = E*II = π ab3/4

Role of the follicle form

10

Franz-J.Wortmann

Gel-like, stable, straight form

Increasing metastability due to cell segmentation

Collapse into equilibrium fibre shape upon cross-linking and drying.

African Hair Follicles (Bernard, 2003)

Hair, emerging from a curved follicle, generallyshows retro-curvature.

If this effect is insufficient or absent, dermatologicalconsequences may occur. https://www.dermquest.com/image-library/image/5044bfcfc97267166cd62ae1

pseudofolliculitis barbae

6

Follicle activities

11Franz J.Wortmann

Different cortical protein types areformed with lateral segregation.

Langbein, 2003Other source:Thibaut et al., 2007

Adhikari et al., 2016

A huge number of processes occurs in the follicle undergenetic control.

Those contributing to hair form need to relate to

• IF-aggregation• lateral cell segregation

12

Biomechanics of hair forms: Primary cases

Franz-J.Wortmann

straight wavy curlystraight

http://stylesatlife.com/articles/different-hair-types/

Medium ellipticity &biased distribution: Slight/medium curl

High ellipticity&bilateral distribution: Strong curl

No or Low ellipticity &random distribution of cell types: Straight Hair

7

Thank you for your attention!

13

Franz-J.Wortmann