University team ups hair conditioner research

Specially developed equipment enabled Bharat Bhushan and his team to get an unprecedented close-up of a series of 'bad hair days' - from chemically overprocessed locks to curls kinked up by humidity.

The technique was used to test a new high-tech hair conditioner. But the same techniques could be used to improve lipstick, nail polish and other beauty products, said Bhushan, Ohio Eminent Scholar and the Howard Winbigler Professor of mechanical engineering at Ohio State.

Bhushan and his team have specialised ins nanotribology - the measurement of very small matter, such as the friction between moving parts in microelectronics.

Hair would have seemed like an unlikely subject to study, but Bhushan said he was invited to give a lecture to a group of Proctor & Gamble scientisits.

"It turns out that, for hair, friction is a major issue,"​ he said.

Activities such as brushing, dying and styling cause friction on the hair follicles, leading to wear and tear that can often be damaging. Although Bhushan said that the subject matter is very different to working with tiny motors, the principle is exactly the same.

"We realized that beauty care was an emerging area for us and we should dive in,"​ Bhushan said.

Ohio State engineers examined hairs under an atomic force microscope (AFM), a tool that let them scratch the surface of hairs and probe inside the hair shaft with a very tiny needle.

The study found that hair conditioners do not always evenly cover the entire hair shaft - a big problem for the product's efficacy.

In response, P&G has recently developed a new formula with additives to make the conditioner coat the hair evenly. The Ohio team found that the new conditioner did coat hair more evenly - the first time such efficacy has been categorically proven.

The next step in the research was to examine healthy and damaged hairs under an electron microscope and an AFM, and to then simulate everyday wear and tear by rubbing hairs together and against polyurethane film to simulate skin.

"We didn't know what we were looking for,"​ Bhushan said. "People know a lot about hair, but nobody has used an AFM to really study the structure of hair… we didn't know what to expect."​

It is already commonly known that damaged hair cuticles begin to peel away from the shaft, creating unmanageable and lack-luster hair. The next step was to find out why and exactly what determines this damage.

The researchers simulated what happens when damaged hair is exposed to humidity; the hairs plump up, and the cuticles stick out even further, leading to frizz. More frizz meant more friction - a fact confirmed by the AFM as researchers dragged a tiny needle across the surface.

Conditioner tends to stick to the cuticle edges, and can make the hair sticky on the nanometer scale. The researchers determined that by poking the hair shaft with the needle, and measuring the force required to pull it away.

They also probed inside hairs to measure the hardness of different layers of the shaft. Hair has a very complex structure, Bhushan said, and these first ultra-precise measurements of interior structure could one day lead to new products that treat hair from the inside.

In the future, he thinks that the AFM techniques could be used to develop wear-resistant nail polishes and lipsticks.