New research from Virginia Tech aims to cut down on that waste \u2013 and consumer frustration \u2013 with a novel approach to creating super slippery industrial packaging. The study,\u00a0which was published in Scientific Reports and has yielded a provisional patent, establishes a method for wicking chemically compatible vegetable oils into the surfaces of common extruded plastics.<\/p>\n
Not only will the technique help sticky foods release from their packaging much more easily, but for the first time, it can also be applied to inexpensive and readily available plastics such as polyethylene and polypropylene.<\/p>\n
These hydrocarbon-based polymers make up 55 percent of the total demand for plastics in the world today, meaning potential applications for the research stretch far beyond just ketchup packets. They're also among the easiest plastics to recycle.<\/p>\n
\u201cPrevious SLIPS, or slippery liquid-infused porous surfaces, have been made using silicon- or fluorine-based polymers, which are very expensive,\u201d said Ranit Mukherjee, a doctoral student in the Department of Biomedical Engineering and Mechanics within the College of Engineering\u00a0and the study\u2019s lead author. \u201cBut we can make our SLIPS out of these hydrocarbon-based polymers, which are widely applicable to everyday packaged products.\u201d<\/p>\n
First created by Harvard University researchers in 2011, SLIPS are porous surfaces or absorbent polymers that can hold a chemically compatible oil within their surfaces via the process of wicking. These surfaces are not only very slippery, but they\u2019re also self-cleaning, self-healing, and more durable than traditional superhydrophobic surfaces.<\/p>\n
In order for SLIPS to hold these oils, the surfaces must have some sort of nano- or micro-roughness, which keeps the oil in place by way of surface tension. This roughness can be achieved two ways: the surface material is roughened with a type of applied coating, or the surface material consists of an absorbent polymer. In the latter case, the molecular structure of the material itself exhibits the necessary nano-roughness.<\/p>\n
Both techniques have recently gained traction\u00a0with startups<\/a>\u00a0and in limited commercial applications. But current SLIPS that use silicone- and fluorine-based absorbent polymers aren\u2019t attractive for industrial applications due to their high cost, while the method of adding roughness to surfaces can likewise be an expensive and complicated process.<\/p>\n \u201cWe had two big breakthroughs,\u201d said Jonathan Boreyko, an assistant professor of biomedical engineering and mechanics and a study co-author. \u201cNot only are we using these hydrocarbon-based polymers that are cheap and in high demand, but we don\u2019t have to add any surface roughness, either. We actually found oils that are naturally compatible with the plastics, so these oils are wicking into the plastic itself, not into a roughness we have to apply.\u201d<\/p>\n In addition to minimizing food waste, Boreyko cited other benefits to the improved design, including consumer safety and comfort.<\/p>\n \u201cWe\u2019re not adding any mystery nanoparticles to the surfaces of these plastics that could make people uncomfortable,\u201d he said. \u201cWe use natural oils like cottonseed oil, so there are no health concerns whatsoever. There\u2019s no fancy recipe required.\u201d<\/p>\n While the method has obvious implications for industrial food and product packaging, it could also find widespread use in the pharmaceutical industry. The oil-infused plastic surfaces are naturally anti-fouling, meaning they resist bacterial adhesion and growth.<\/p>\n Although the technique may sound very high-tech, it actually finds its roots in the pitcher plant, a carnivorous plant that entices insects to the edge of a deep cavity filled with nectar and digestive enzymes. The leaves that form the plant\u2019s eponymous shape have a slippery ring, created by a secreted liquid, around the periphery of the cavity. When the insects move onto this slippery ring, they slide into the belly of the plants.<\/p>\n \u201cThis slippery periphery on the pitcher plant actually inspired our SLIPS product,\u201d said Mukherjee.<\/p>\n The pitcher plant\u2019s innovation \u2013 which engineers are now copying with great success \u2013 is the combination of a lubricant with some type of surface roughness that can lock that lubricant into place very stably with surface tension.<\/p>\n \u201cWe\u2019re taking that same concept, but the roughness we\u2019re using is just a common attribute of everyday plastics, which means maximal practicality,\u201d said Boreyko.<\/p>\n This research was fully funded through an industrial collaboration with Bemis North America.\u00a0Additional co-authors of the study include Mohammad Habibi, a Virginia Tech mechanical engineering graduate student; Ziad Rashed, an engineering science and mechanics 2018 graduate from Virginia Tech\u2019s undergraduate program; and Otacilio Berbert and Xiangke Shi, both of Bemis North America.<\/p>\n Source:\u00a0https:\/\/vtnews.vt.edu\/articles\/2018\/07\/super-slippery-packaging-reduces-food-waste.html<\/a><\/p>\n