Trinity College Dublin Enlists Biomechanics To Aid Haircare Research

Above is an electron microscope image of a hair, split along its length (Photo: Prof. David Taylor, Trinity College Dublin).

A group at Trinity College Dublin, led by Professor David Taylor, has devised a machine that recreates what happens when tangled hair is combed out. Their work will may help hair care experts gain a greater understanding of split ends and treatments.

While natural materials have been studied, working with hair was a first for Prof. Taylor’s research at Trinity Centre for Biomedical Engineering.

That request came from L’Oréal, according to the college.

The team set out to devise experiments to generate splitting under laboratory conditions in order to quantify the effects of hair type and treatment on the tendency to form splits.

Results of their work has been published in the Journal of the Royal Society Interface Focus. The article, “The biomechanics of splitting hairs,” was published on May 10.

The team says it developed three new tests—known as “loop tensile,” “moving loop” and “moving loop fatigue”—aiming to simulate the mechanical environment of tangles of hair strands during combing. The team tested straight strands of human hair, comparing low-quality hair (from a subject who experienced split ends) with hair from a control (non-splitting) subject.

The abstract states: “Significant differences were found, especially in the moving loop fatigue test where the low-quality hair failed in fewer cycles. Splitting occurred in both types of hair, but with the crucial difference that in the low-quality hair, splits originated inside the hair strand and propagated longitudinally over considerable distances, while in the control hair, splits originated at the strand surface and remained short. Bleaching of the control hair changed its behavior, making it similar to that of the low-quality hair. Some simple calculations emphasized the role of longitudinal shear stress and shear stress intensity in generating microcracks which could then propagate within the moving loop, paving the way for a future theoretical model of the splitting mechanism.”

“This work constitutes a first step in developing a scientific approach to better understanding the biomechanics of hair splitting. It paves the way for future studies, including a more comprehensive experimental program involving a larger number of donors with different hair types – including curly hair – and more detailed studies that could incorporate the effects of humidity, temperature and different treatments,” said Prof. Taylor.