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Nanoindentation study of human fingernail for determining its structural elasticity
Hironori Tohmyoh1, Masaru Abukawa1
1Department of Finemechanics, Graduate School of Engineering, Tohoku University, Sendai, Japan.
Summary
Human nails have a three-layered structure influencing their mechanical properties. Researchers developed a method to measure nail structural elasticity, finding it softer than hair and affected by softening treatments.
Area of Science:
- Biomechanics
- Materials Science
- Dermatology
Background:
- Human nails are crucial for force transmission to fingertips.
- Nail mechanical properties are important indices, but their layered structure's impact is understudied.
- The nail's three-layered structure (dorsal, intermediate, ventral plates) is hypothesized to influence mechanical properties.
Purpose of the Study:
- To investigate the mechanical properties of human nails based on their layered structure.
- To develop a method for estimating the structural elasticity of human nails.
- To compare the deformability of human nails with human hair and assess the impact of softening treatments.
Main Methods:
- Nanoindentation was used to measure the Young's moduli of the top, middle, and under nail plates.
- A theoretical model was developed to estimate structural elasticity for bending deformation.
- Structural elasticity was compared to human hair, and the effect of urea cream softening treatment was evaluated.
Main Results:
- The Young's moduli of the nail plates were measured: dorsal (2.9 GPa), intermediate (3.1 GPa), and ventral (2.8 GPa).
- The estimated structural elasticity of the human nail was 2.9 GPa, approximately 75% of human hair's elasticity.
- Softening treatment with urea cream reduced nail structural elasticity by 30%.
Conclusions:
- A novel method for estimating the structural elasticity of three-layered human nails was proposed.
- Structural elasticity, measured in Pascals, allows quantitative comparison with other materials and treatment effects.
- This index provides a valuable tool for understanding nail biomechanics and the impact of interventions.
