A team of researchers at the Ohio State University say they have created the perfect texture for hair care and other personal care bottles, enabling any type of soap-based product to flow freely.
The patent-pending technology has been described in an article published in the journal Philosophical Transactions of the Royal Society, which highlights how the eternal problem of ‘sticky’ shampoo formulas can be overcome and help to keep consumers happier.
Surfactants make shampoos 'sticky'
The problem arises from the significant amount of surfactants that are used in most shampoo formulas. This in turn creates surface tension and means the molecules of a substance bind together closely, which also gives the formula greater adhesion to contact surfaces.
To resolve the problem the team developed a method that involves lining a plastic bottle with microscopic y-shaped structures that cradle droplets of soap above tiny air pockets, which means the liquid formula actually never touches the bottle’s surface.
The y-shaped particles are achieved using nanoparticles made of silica or quartz, which, when treated on the surface of polypropylene packaging materials, means that the surface will not stick with the soap.
A simple an inexpensive technology
Although the solution to the problem sounds complex, project leaders Bharat Bhushan and Philip Brown say that the solution is actually relatively simple and relatively inexpensive compared to other alternative surface treatments.
It just requires a small amount of solvent and ultra-fine silica nanoparticles to be sprayed on the inside of the bottles. This process enables the propylene to be softened just enough to embed the silica on the surface before it hardens again and remains on the surface.
This means that instead of sticking to the surface of the bottle, the shampoo formulation forms into beads and simply drops off the surface of the bottle.
"It's what you'd call a first-world problem, right? 'I can't get all of the shampoo to come out of the bottle.' But manufacturers are really interested in this, because they make billions of bottles that end up in the garbage with product still in them," said Bhushan, Ohio Eminent Scholar and Howard D. Winbigler Professor of mechanical engineering at Ohio State.
Catching up with tomato ketchup
Such technology already exists in the food industry for products like the packaging for tomato ketchup, but the team said that there appeared to be a gap in the market for a solution to meet the needs of the personal care industry.
In addition to the obvious advantages to consumers, the research team also claims that the technology could help aid recycling, simply because it would cut down on the amount of rinsing necessary before the used shampoo bottle is recycled.
"We all struggle with shampoo bottles at home," Bhushan said. "I have a few in my shower right now. Trying to get the last drop out, I put it upside down, and my wife adds water to the bottle and fights with it for a while, and then we give up and just throw it away."
The team now says it is working towards licensing the coating technique for a range of personal care products, together with other applications such as biomedical devices and catheters.