Despite the increasing availability of new hair care products within the past century, many products are inadequate for tackling today's rigorous hair treatments.
"For the first time, we present an experimental set-up that allows measuring the subtle forces, both physical and chemical, that arise when single hairs slide past each other or are pressed against each other," said Eva Max, a doctoral student in chemistry at the University of Bayreuth.
"The findings will help provide clearer strategies for optimising hair care products," she added.
In the new study, the researchers invented a unique technology for analysing hair that involves mounting individual hair fibres on a cantilever tip of an atomic force microscope and measuring their interactions as they touch each other.
"The system will allow scientists to explore how different hair care products affect hair-to-hair interactions so that these products can be optimised in a more systematic fashion," said Max.
With the help of the new technique the researchers analysed hair samples collected from volunteers, which were previously bleached, ranged from light blond to dark blonde in colour.
The researchers found that hair felt rough and difficult to comb for two main reasons. On the one hand, mechanical damage to a hair's surface, or cuticle, creates scaly projections that jut out at perpendicular angles to other hair fibres.
When hair fibres slide past each other, these scales create more friction than smooth hairs, causing a rough feel and making hair more difficult to comb.
To soften hair, according to the researchers, conditioners must contain active agents to smooth-out these scales so that they produce less friction.
On the other hand, chemical changes occur when hair fibres interact. Negative charges build up on the surface of hair that causes repulsion between single hairs. This repulsion causes friction and makes hair rough and difficult to comb. To solve the problem, positively-charged polymers that neutralize the negatively charged surfaces are included in conditioner formula to provide a silky feel to hair.
The key to repairing these processes is to find the right ratio of beneficial components in a conditioner or shampoo that optimize hair feel, Max and colleagues say.
This new method will allow developers of hair care products to achieve this goal more easily, giving consumers a more reliable product, the researchers say.
The study was presented at the American Chemical Society's 236th National Meeting.