Original title: Hair is a functionally graded composite, not a uniform fiber
Andrew K. Schulz, Svetlana Griego, Vesna Srot, Giulia Ballardini +10 · July 2026
People usually think of hair as a simple, uniform thread made purely of keratinA fibrous protein that makes up hair, nails, and similar structures. protein. Researchers wanted to know how hair achieves different physical tasks along its length. To find out, they examined whiskers and body hairs from the domestic cat. They discovered that hair is actually a complex composite material that changes from end to end. Three key structures change along each hair: the layered outer wall, tiny pigment-like granules inside, and calcium inside those granules. These granules line up in channels that may reinforce the hair. Where more granules appear, the hair’s local mechanical properties shift. Chemical treatments that stripped calcium and broke down the hair caused bases to harden while tips split, proving hair is not uniform.
Imagine a rope made by braiding strands of different thicknesses. If you assume the whole rope is the same, you might grip it at the wrong spot and be surprised when one end is stiff and the other bends easily. In this paper, hair is like that rope: the protein structure, the tiny particles embedded in it, and the calcium inside those particles all change from base to tip, so each section of the hair behaves differently.
If hair is a graded material rather than a uniform one, then how it breaks, feels, and responds to chemicals depends on where along the strand you look. That matters for understanding how hair performs its biological roles, from protection to sensory perception, and why chemical treatments damage some parts of hair more than others. It also shifts how biologists think about a material made purely of keratin.
The abstract reports correlations, not proof of causation: granule prevalence correlates with local mechanical properties, but the paper does not establish that the granules cause those differences. It also focuses on domestic cat hairs and whiskers, so the findings may not generalize to other species. The chemical treatment results are described for body hairs only, not whiskers. The abstract does not quantify the stiffness variation in cats or provide a full mechanical map.
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Hair is a functionally graded composite, not a uniform fiber — Andrew K. Schulz, Svetlana Griego, Vesna Srot et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.