Bio-inspired surface ensures sticky liquids do not go to waste

Scientists from The Ohio State University have been able to squeeze the last drop of shampoo out of a bottle, thanks to a bio-inspired surface they created. The surface ensures that sticky liquids such as detergent and shampoo slide cleanly out of their bottles.

The technique involves lining a plastic bottle with microscopic y-shaped structures cradling the droplets of soap aloft above tiny air pockets. This ensures the soap never really touches the inside of the bottle. Small nanoparticles such as quartz or silica are used to make the “y” structures. When treated, they don’t stick to soap.

Engineers Bharat Bhushan and Philip Brown took a lot of trouble to solve this problem though the solution they found is simpler and cheaper than other alternatives under development elsewhere. Moreover, this new method works for a common plastic, polypropylene, used to package household goods and food stuffs.

As one of the most slippery surfaces in nature is the lotus leaf, known to repel water, the scientists used modelling to adapt lotus leaf's air pocket system to design an unbelievably slippery surface. Even low surface-tension liquids such as shampoo will also slide along the slipper surface created.

“We've been working in the field of bio-inspired surfaces for some 10 years ... The way the lotus-inspired surface works is that you need a certain roughness to create air pockets,” lead researcher professor Bharat Bhushan told the ABC.

In order to attach the slippery surface to polypropylene plastic shampoo bottles, the scientists mixed silica nanoparticles in a solvent. Next, they sprayed the mixture onto the surface of the polypropylene. The scientists were able to create the extremely slippery surface as the solvent softened and dissolved the surface of the plastic. The silicate particles got embedded and produced the desired air pockets.

Shampoo was used to test the surface and it slid off right away. However, more research is needed to make the effect ever-lasting as the surface became less repellent over time. The study was published in Philosophical Transactions of the Royal Society.