Rethinking Ketchup Packets: New Approach to Slippery Packaging Aims to Cut Food Waste

Benefits Also Include Consumer Safety and Comfort

Date: August 3, 2018
Source: Virginia Tech
Summary: New research aims to cut down on waste -- and consumer frustration -- with a novel approach to creating super slippery industrial packaging. The study establishes a method for wicking chemically compatible vegetable oils into the surfaces of common extruded plastics, like those used for ketchup packets and other condiments.

Virginia Tech doctoral student Ranit Mukherjee observes a dollop of ketchup as it moves on a super slippery plastic film. Mukherjee is the lead author on a study that yielded a novel approach to creating super slippery industrial packaging.
Credit: Virginia Tech

Almost everyone who eats fast food is familiar with the frustration of trying to squeeze every last drop of ketchup out of the small packets that accompany french fries.

What most consumers don't realize, however, is that food left behind in plastic packaging is not simply a nuisance. It also contributes to the millions of pounds of perfectly edible food that Americans throw out every year. These small, incremental amounts of sticky foods like condiments, dairy products, beverages, and some meat products that remain trapped in their packaging can add up to big numbers over time, even for a single household.

New research from Virginia Tech aims to cut down on that waste -- and consumer frustration -- with a novel approach to creating super slippery industrial packaging.

The study, which 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.

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.

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.

"Previous SLIPS, or slippery liquid-infused porous surfaces, have been made using silicon- or fluorine-based polymers, which are very expensive," said Ranit Mukherjee, a doctoral student in the Department of Biomedical Engineering and Mechanics within the College of Engineering and the study's lead author. "But we can make our SLIPS out of these hydrocarbon-based polymers, which are widely applicable to everyday packaged products."

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're also self-cleaning, self-healing, and more durable than traditional superhydrophobic surfaces.

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.

Both techniques have recently gained traction with startups and in limited commercial applications. But current SLIPS that use silicone- and fluorine-based absorbent polymers aren't 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.

"We had two big breakthroughs," said Jonathan Boreyko, an assistant professor of biomedical engineering and mechanics and a study co-author. "Not only are we using these hydrocarbon-based polymers that are cheap and in high demand, but we don't 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."

In addition to minimizing food waste, Boreyko cited other benefits to the improved design, including consumer safety and comfort.

"We're not adding any mystery nanoparticles to the surfaces of these plastics that could make people uncomfortable," he said. "We use natural oils like cottonseed oil, so there are no health concerns whatsoever. There's no fancy recipe required."

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.

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's 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.

"This slippery periphery on the pitcher plant actually inspired our SLIPS product," said Mukherjee.

The pitcher plant's innovation -- which engineers are now copying with great success -- is the combination of a lubricant with some type of surface roughness that can lock that lubricant into place very stably with surface tension.

"We're taking that same concept, but the roughness we're using is just a common attribute of everyday plastics, which means maximal practicality," said Boreyko.

This research was funded through an industrial collaboration with Bemis North America. Additional 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's undergraduate program; and Otacilio Berbert and Xiangke Shi, both of Bemis North America.



Reprinted From:
Virginia Tech. "Rethinking ketchup packets: New approach to slippery packaging aims to cut food waste: Benefits also include consumer safety and comfort." ScienceDaily. ScienceDaily, 3 August 2018. https://www.sciencedaily.com/releases/2018/08/180803103302.htm

Structure of 'Concrete Disease' Solved

Previously undocumented sheet-silicate crystal structure

Date: November 5, 2015
Source: Swiss Federal Laboratories for Materials Science and Technology (EMPA)
Summary: When bridges, dam walls and other structures made of concrete are streaked with dark cracks after a few decades, the culprit is AAR: the alkali-aggregate reaction. AAR damages concrete structures all over the world and makes complex renovations or reconstructions necessary. Researchers have now solved the structure of the material produced in the course of AAR at atomic Level.


Researchers from the Paul Scherrer Institute (PSI) teamed up with colleagues from the Swiss Materials Science Lab Empa to study a degenerative sign of ageing in concrete: the so-called alkali-aggregate reaction (AAR). In the course of AAR, a material forms that takes up more space than the original concrete and thus gradually cracks the concrete from within as the decades go by.

The researchers have now explored the exact structure of this material. They managed to demonstrate that its atoms are arranged extremely regularly, making it a crystal. They also showed that the structure of this crystal is a so-called sheet-silicate structure. This specific structure had never been observed before. The researchers made their discovery thanks to measurements at the Swiss Light Source SLS at PSI. The research results could help towards the development of more durable concrete in future.

A Global Problem

AAR is a chemical reaction that affects outdoor concrete structures all over the world. It happens when concrete is exposed to water or moisture. For instance, numerous bridges and up to twenty per cent of the dam walls in Switzerland are affected by AAR. With AAR, the basic ingredients in the concrete are actually the problem: cement -- the main component of concrete -- contains alkali metals such as sodium and potassium. Any moisture infiltrating the concrete -- stemming for example from rainwater -- reacts with these alkali metals, leading to an alkaline solution.

The second main ingredient in concrete is sand and gravel, which in turn are composed of minerals, such as quartz or feldspar. Chemically speaking, these minerals are so-called silicates. The alkaline water reacts with these silicates and forms a so-called alkali calcium silicate hydrate. This is itself able to absorb more moisture, which causes it to expand and gradually crack the concrete from within. This entire process is referred to as AAR.

AAR takes place extremely slowly, so that the cracks are initially only tiny and invisible to the naked eye. Over the course of three or four decades, however, the cracks widen significantly and eventually jeopardise the durability of the entire concrete structure.

A New Crystal

Even if the chemical processes involved in AAR have long been known, nobody had identified the physical structure of the alkali calcium silicate hydrate formed in the course of AAR. The researchers at PSI and Empa have now managed to fill this knowledge gap. They studied the substance of a Swiss bridge constructed in 1969, which has been affected heavily by AAR. Researchers from Empa cut out a material sample from the bridge and ground down a small piece of it until they were left with a wafer-thin sample that was merely 0.02 millimetres thick. The sample was then taken to the Swiss Light Source SLS and irradiated with an extremely narrow x-ray beam, fifty times thinner than a human hair. Performing so-called diffraction measurements and a complex data analysis, the PSI researchers were eventually able to determine the crystal structure of the material with pinpoint precision.

They found that the alkali calcium silicate hydrate has a previously undocumented sheet-silicate crystal structure. "Normally, discovering an uncatalogued crystal structure means you get to name it," explains Rainer Dähn, the first author of the study. "But it has to be a crystal found in nature, therefore we didn't get that honour," says the researcher with a smile. Andreas Leemann, Head of the Concrete Technology Group at Empa, had the idea for the current study. The researchers from PSI then brought their knowledge of the x-ray beam method to the table. "In principle, it's possible to add organic materials to the concrete that are able to reduce the build-up of tension," explains materials scientist Leemann. "Our new results provide a scientific basis for these considerations and could pave the way for the development of new materials.

Story Source: Swiss Federal Laboratories for Materials Science and Technology (EMPA). "Structure of 'concrete disease' solved: Previously undocumented sheet-silicate crystal structure." ScienceDaily. ScienceDaily, 5 November 2015. .