Research Papers

Determination of the Structural Elasticity of Human Fingernails by Bending Test and Comparison With the Structural Elasticity of Human Hair

[+] Author and Article Information
Hironori Tohmyoh

Department of Finemechanics,
Tohoku University,
Aoba 6-6-01, Aramaki,
Aoba-ku, Sendai 980-8579, Japan
e-mail: tohmyoh@ism.mech.tohoku.ac.jp

Daiki Taniguchi

Department of Finemechanics,
Tohoku University,
Aoba 6-6-01, Aramaki,
Aoba-ku, Sendai 980-8579, Japan

Manuscript received November 22, 2018; final manuscript received February 19, 2019; published online April 1, 2019. Assoc. Editor: Seyed Allameh.

ASME J of Medical Diagnostics 2(3), 031001 (Apr 01, 2019) (7 pages) Paper No: JESMDT-18-1059; doi: 10.1115/1.4042926 History: Received November 22, 2018; Revised February 19, 2019

A bending test scheme for accurately determining the structural elasticity of human nails is reported. The structural elasticity expresses the deformability of a multilayered material for bending, and it is the flexural rigidity without depending on the external dimensions. The human nail samples used in this study were prepared from the free ends of the nails and are, therefore, curved, so the equation to determine the structural elasticity was derived from elastic, curved beam theory. The structural elasticity of the nail samples determined by the bending tests was found to be 2.19 GPa, and this value decreased by about 50% when nail polish was put on the nails. Lower value of the Young's modulus of the nail polish was found to cause decrease in the structural elasticity of the sample. Moreover, we also measured the structural elasticity of samples of hair prepared from the same person by the bending tests. Surprisingly, the structural elasticity of the hair (4.37 GPa) was found to be twice that of the nails.

Copyright © 2019 by ASME
Your Session has timed out. Please sign back in to continue.


Jindrich, D. L. , Zhou, Y. , Becker, T. , and Dennerlein, J. T. , 2003, “ Non-Linear Viscoelastic Models Predict Fingertip Pulp Force-Displacement Characteristics During Voluntary Tapping,” J. Biomech., 36(4), pp. 497–503. [CrossRef] [PubMed]
Sakai, N. , and Shimawaki, S. , 2007, “ Strain in the Nail at Fingertip Compression,” Skin Res. Technol., 13(4), pp. 449–453. [CrossRef] [PubMed]
Shimawaki, S. , Nakayama, A. , Nakabayashi, M. , and Sakai, N. , 2015, “ Thumbnail Strain During Pressing and Plucking of a String,” J. Biomech. Sci. Eng., 10(3), pp. 1–10.
Spearman, R. I. C. , 1985, “ Phylogeny of the Nail,” J. Hum. Evol., 14(1), pp. 57–61. [CrossRef]
Helmdach, M. , Thielitz, A. , Röpke, E.-M. , and Gollnick, H. , 2000, “ Age and Sex Variation in Lipid Composition of Human Fingernail Plates,” Skin Pharmacol. Appl. Skin Physiol., 13(2), pp. 111–119. [CrossRef] [PubMed]
Jeong, K. H. , Kim, K. S. , Lee, G. L. , Choi, S. J. , Jeong, T. J. , Shin, M.-K. , Park, H. K. , Sim, W. Y. , and Lee, M.-H. , 2011, “ Investigation of Aging Effects in Human Hair Using Atomic Force Microscopy,” Skin Res. Technol., 17(1), pp. 63–68. [CrossRef] [PubMed]
Berker, D. , 2013, “ Nail Anatomy,” Clin. Dermatol., 31, pp. 509–515. [CrossRef] [PubMed]
Shemer, A. , and Daniel, C. R., III , 2013, “ Common Nail Disorders,” Clin. Dermatol., 31(5), pp. 578–586. [CrossRef] [PubMed]
Golasik, M. , Przybyłowicz, A. , Woźniak, A. , Herman, M. , Gawęcki, W. , Golusiński, W. , Walas, S. , Krejpcio, Z. , Szyfter, K. , Florek, E. , and Piekoszewski, W. , 2015, “ Essential Metals Profile of the Hair and Nails of Patients With Laryngeal Cancer,” J. Trace Elem. Med. Biol., 31, pp. 67–73. [CrossRef] [PubMed]
Forte, G. , Alimonti, A. , Violante, N. , Gregorio, M. D. , Senofonte, O. , Petrucci, F. , Sancesario, G. , and Bocca, B. , 2005, “ Calcium, Copper, Iron, Magnesium, Silicon and Zinc Content of Hair in Parkinson's Disease,” J. Trace Elem. Med. Biol., 19(2–3), pp. 195–201. [CrossRef] [PubMed]
Moran, P. , Towler, M. R. , Chowdhury, S. , Saunders, J. , German, M. J. , Lawson, N. S. , Pollock, H. M. , Pillay, I. , and Lyons, D. , 2007, “ Preliminary Work on the Development of a Novel Detection Method for Osteoporosis,” J. Mater. Sci.: Mater. Med., 18(6), pp. 969–974. [CrossRef] [PubMed]
Hossein-Nezhad, A. , Afjeh, M. S. , Saghafi, H. , Rahmani, M. , Parviz, M. , Maghbooli, Z. , and Larijani, B. , 2008, “ The Fingernail Protein Content May Predict Bone Turnover in Postmenopausal Women,” Iran. J. Public Health, 37(1), pp. 55–62.
Cummins, N. M. , Day, J. C. C. , Wren, A. , Carroll, P. , Murphy, N. , Jakeman, P. M. , and Towler, M. R. , 2010, “ Raman Spectroscopy of Fingernails: A Novel Tool for Evaluation of Bone Quality?,” Spectroscopy, 24(5), pp. 517–524. [CrossRef]
Beattie, J. R. , Cummins, N. M. , Caraher, C. , O'Driscoll, O. M. , Bansal, A. T. , Eastell, R. , Ralston, S. H. , Stone, M. D. , Pearson, G. , and Towler, M. R. , 2016, “ Raman Spectroscopic Analysis of Fingernail Clippings Can Help Differentiate Between Postmenopausal Women Who Have and Have Not Suffered a Fracture,” Clin. Med. Insights: Arthritis Musculoskeletal Disord., 9, pp. 109–116. [CrossRef]
Beyak, R. , Kass, G. S. , and Meyer, C. F. , 1971, “ Elasticity and Tensile Properties of Human Hair—Part II: Light Radiation Effects,” J. Soc. Cosmet. Chem., 22(10), pp. 667–678. http://journal.scconline.org/abstracts/cc1971/cc022n10/p00667-p00678.html
Seshadri, I. P. , and Bhushan, B. , 2008, “ In Situ Tensile Deformation Characterization of Human Hair With Atomic Force Microscopy,” Acta Mater., 56(4), pp. 774–781. [CrossRef]
Erik, B. , Havitcioglu, H. , Aktan, S. , and Karakus, N. , 2008, “ Biomechanical Properties of Human Hair With Different Parameters,” Skin Res. Technol., 14(2), pp. 147–151. [CrossRef] [PubMed]
Yu, Y. , Yang, W. , Wang, B. , and Meyers, M. A. , 2017, “ Structure and Mechanical Behavior of Human Hair,” Mater. Sci. Eng. C, 73, pp. 152–163. [CrossRef]
Parbhu, A. N. , Bryson, W. G. , and Lal, R. , 1999, “ Disulfide Bonds in the Outer Layer of Keratin Fibers Confer Higher Mechanical Rigidity: Correlative Nano-Indentation and Elasticity Measurement With an AFM,” Biochemistry, 38(36), pp. 11755–11761. [CrossRef] [PubMed]
Sogabe, A. , Yasuda, M. , and Noda, A. , 2002, “ Physical Properties of Human Hair 1-Evaluation of Bending Stress by Measuring the Major and the Minor Axis of Human Hair,” J. Soc. Cosmet. Chem. Jpn., 36(3), pp. 207–216. [CrossRef]
Tohmyoh, H. , Ishihara, M. , Akanda, M. A. S. , Yamaki, S. , Watanabe, T. , and Iwabuchi, T. , 2011, “ Accurate Determination of the Structural Elasticity of Human Hair by a Small-Scale Bending Test,” J. Biomech., 44(16), pp. 2833–2837. [CrossRef] [PubMed]
Farran, L. , Ennos, A. R. , Starkie, M. , and Eichhorn, S. J. , 2009, “ Tensile and Shear Properties of Fingernails as a Function of a Changing Humidity Environment,” J. Biomech., 42(9), pp. 1230–1235. [CrossRef] [PubMed]
Farran, L. , Ennos, A. R. , and Eichhorn, S. J. , 2008, “ The Effect of Humidity on the Fracture Properties of Human Fingernails,” J. Exp. Biol., 211(Pt. 23), pp. 3677–3681. [CrossRef] [PubMed]
Wei, P. , Qian, L. , Zheng, J. , and Zhou, Z. , 2010, “ Effect of Water on the Mechanical and Frictional Behaviors of Human Fingernails,” Tribol. Lett., 38(3), pp. 367–375. [CrossRef]
Farren, L. , Shayler, S. , and Ennos, A. R. , 2004, “ The Fracture Properties and Mechanical Design of Human Fingernails,” J. Exp. Biol., 207(Pt. 5), pp. 735–741. [CrossRef] [PubMed]
Howard, P. B. , 1970, “ The Physical Properties of Nail,” J. Invest. Dermatol., 55(2), pp. 115–122. [CrossRef] [PubMed]
Tohmyoh, H. , Akanda, M. A. S. , and Saka, M. , 2011, “ Small-Span Bending Test for Determination of Elastic-Plastic Properties of Ultrathin Pt Wires,” Appl. Phys. A, 103(2), pp. 285–291. [CrossRef]
Akanda, M. A. S. , Tohmyoh, H. , and Saka, M. , 2010, “ An Integrated Compact Unit for Wide Range Micro-Newton Force Measurement,” J. Solid Mech. Mater. Eng., 4(4), pp. 545–556. [CrossRef]
Swift, J. A. , and Smith, J. R. , 2000, “ Atomic Force Microscopy of Human Hair,” Scanning, 22(5), pp. 310–318. https://www.ncbi.nlm.nih.gov/pubmed/11023235 [PubMed]
Dawber, R. P. R. , 1980, “ The Ultrastructure and Growth of Human Nails,” Arch. Dermatol. Res., 269(2), pp. 197–204. [CrossRef] [PubMed]
Vejnovic, I. , Simmler, L. , and Betz, G. , 2010, “ Investigation of Different Formulations for Drug Delivery Through the Nail Plate,” Int. J. Pharm., 386(1–2), pp. 185–194. [CrossRef] [PubMed]
Dias, D. T. , Steimacher, A. , Bento, A. C. , Neto, A. M. , and Baesso, M. L. , 2007, “ Thermal Characterization In Vitro of Human Nail: Photoacoustic Study of the Aging Process,” Photochem. Photobiol., 83(5), pp. 1144–1148. [CrossRef] [PubMed]
Tohmyoh, H. , Ishihara, M. , Ikuta, K. , and Watanabe, T. , 2018, “ On the Correlation Between the Curvature of the Human Eyelash and Its Geometrical Features,” Acta Biomater., 76, pp. 108–115. [CrossRef] [PubMed]


Grahic Jump Location
Fig. 1

(a) Sample preparation procedure and (b) cross section through a nail

Grahic Jump Location
Fig. 2

Schematic of the bending test for a curved beam

Grahic Jump Location
Fig. 3

(a) Test platform and (b) typical structure of the force sensor. The sensor is comprised of a double-beam cantilever, a probe for applying the load, and a capacitance sensor. (c) Details of A in (a), where the load was applied to the outer surface of the nail toward the center of curvature.

Grahic Jump Location
Fig. 4

Experimental results from human nail samples: (a) examples of P–δ relationships for samples without nail polish, (b) examples of P–δ relationships for samples with nail polish, and (c) the relationships between P R3 (θ0 − sinθ0 cosθ0)/(2 I) and δ. The slope of this relationship gives the value of SE in bending, (d) the values of SE of nail samples without nail polish, (e) the values of SE of nail samples with nail polish, and (f) comparison between the average values of SE between the samples without nail polish and those with nail polish.

Grahic Jump Location
Fig. 5

(a) Example of the P–δ relationship of the nail polish sample and (b) the values of E of the nail polish samples

Grahic Jump Location
Fig. 6

The values of SE and FR as functions of hnp/h

Grahic Jump Location
Fig. 7

Experimental results for human hair samples: (a) A photograph of the experimental setup, where the load was applied in the direction of the long axis of the cross section through the sample, (b) examples of P–δ relationships for the human hair samples obtained with the load applied in two different directions, and (c) the relationships between P L3/(3 I) and δ. The slope of this relationship corresponds with SE in bending, (d) the values of SE of the hair samples, and (e) comparison of the average values of SE between the nail and hair samples.

Grahic Jump Location
Fig. 8

Cross section through a hair



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In