You’re in the shower and you reach for the shower gel. There’s only a little quantity of the gel remaining in the plastic bottle. You squeeze, and squeeze, and squeeze again but the last remaining drops won’t come out. Familiar story?
The same thing happens with laundry products too. These may seem like trivial annoyances, but this is a physical property of the bottles used to hold gels and fluids that can be overcome. The reason why this happens is due to surface tension. This is the tendency of the molecules of a substance to stick to each other. At liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other than to the molecules in the air.
Scientists Bharat Bhushan and Philip Brown, based at The Ohio State University (@OhioState), have developed a new texture inside plastic bottles. This is designed to allow soap products flow freely.
The researchers have shown that by lining the interior of the plastic bottles with microscopic y-shaped structures these can suspend the droplets of soap above tiny air pockets. This means the soap or gel does not make contact with the inside of the bottle.
The newly fashioned “y” structures have been developed through the application of nanotechnology. The structures are composed of nanoparticles made of silica or quartz. These particles do not stick to soap and instead repel it, allowing it to travel unhindered when a bottle is inverted of squeezed.
Trails have shown the “y” structures, planted a few micrometers apart, work efficiently with all common types of plastics used to hold household goods, most of which are based on polypropylene.
The new surface, once commercialized, should prevent millions of bottles of shower gel, laundry detergent and liquid soap being discarded as garbage with considerable amounts of the contents remaining in the bottles.
The research has been presented in the journal Philosophical Transactions of the Royal Society. The paper is titled “Durable superoleophobic polypropylene surfaces.”
