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. It means that every drop of liquid soap, shampoo or laundry detergent will be able to be removed.Bharat Bhushan, the study's lead scientist from Ohio State University, 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.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." ..