Sticky problem of pouring out all the shampoo may be solved with new coating

The days of struggling to pour out the last dregs of shampoo or washing up liquid could soon be over.

Scientists have developed a nanoparticle coating for plastic bottles that allows soap products to flow freely.

What this means is that every drop of liquid soap, shampoo or laundry detergent can be removed and none is wasted.

Technology already existed to help food products pour out of containers, but soap is a much stickier problem.

Lead scientist Professor Bharat Bhushan, from Ohio State University in the US, said: "Compared to soaps, getting ketchup out of a bottle is trivial."

His team has developed a way of lining plastic bottles with microscopic Y-shaped structures that cradle droplets of soap above tiny air pockets.

As a result, the soap never actually touches the sides of the bottle. Instead of spreading out, the soap droplets form beads and roll off the surface.

The Y structures are built up using much smaller nanoparticles made from silica or quartz, an ingredient in glass.

Prof Bhushan said: "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.

"We all struggle with shampoo bottles at home. 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 invention could also aid recycling, said the researchers whose patent-pending technology is described in the journal Philosophical Transactions Of The Royal Society.

Before plastic bottles can be recycled they have to be rinsed completely clean.