You shake, fill with water, squeeze and pound. You let it sit upside down for a week or two. Trying to get the final dollop of shampoo out of the bottle can be frustrating. We’ve all been there.
Thankfully for us, engineers from the Ohio State University have now developed a coating for plastic bottles that gets every drop out, like magic.
And, the team says, the patent-pending technology is simpler, cheaper and has a smaller environmental impact than alternatives devised to conquer this sticky dilemma.
Soaps naturally have low surface tension, making them stick to oil and water, hence making us clean in the shower. But that property also makes the soap, shampoo or dish soap stick to the inside of the bottle.
The Ohio State researchers solved the problem by creating a coating devised of a solvent and super-fine silica particles that are sprayed on the inside of bottles during production.
Once the plastics start to harden and set, the silica creates a teeny, tiny layer of super-hard, Y-shaped branches. The layer creates air pockets on the surface of the plastic, which break up the adhesion of the soap. And voilà, the soap slides right off the plastic.
We’ve seen the sticky bottle challenge solved before — a product called LiquiGlide lets mayonnaise and ketchup flow smoothly — but soap is a little different.
“Compared to soaps, getting ketchup out of a bottle is trivial,” said Bharat Bhushan, one of the creators, said in a statement. Foods have a higher surface tension, so they like to stick to each other more than stick to the plastic. But soap, with its very low surface tension, would rather stick to the plastic. So another coating method had to be devised.
Though it may seem like a frivolous endeavor to create a stick-free bottle, the new coating will save soaps from waste, and help smooth the recycling process.
“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.