Nav: Home

Universal stabilization

June 14, 2017

Researchers led by Lucio Isa, Professor of Interfaces, Soft Matter and Assembly at ETH Zurich's Department of Materials, have created a new type of silica particle able to stabilise emulsions in a new way. An emulsion is a finely dispersed mixture of two immiscible liquids, constituted by droplets of one liquid dispersed in the second one. An everyday example of this is a salad dressing made of oil and vinegar: its main constituents, vinegar (effectively water) and oil, do not mix on their own and must be whisked vigorously to create a uniform mixture. If this mixture is left to stand, the finely dispersed vinegar droplets will fuse together again and the liquids will separate out completely.

Different emulsifiers needed

This is why it is necessary to stabilise emulsions; this can be achieved using numerous different emulsifiers, such as surfactants, polymers or proteins. As early as in the beginning of the 1900's, the British chemists W. Ramsden and S. U. Pickering also demonstrated that emulsions could be stabilised using very fine solid particles, such as spherical silica particles (SiO2).

In this process, the particles spontaneously enter and bind to the interface between the two liquids. They form a sort of armour around the droplets and prevent their fusion, thus stabilising the emulsion practically indefinitely. However, until now, this required two types of particles: those with hydrophilic surfaces, i.e. mostly sitting in the water, that stabilise only oil-in-water emulsions and those with hydrophobic surfaces, i.e. mostly sitting in the oil, that stabilise only water-in-oil mixtures.

One emulsifier stabilises both emulsions

Now, this may no longer be necessary: the ETH researchers led by Isa have roughened the surfaces of these tiny silica spheres, which measure one to six micrometres in diameter, by loading them with silica nanoparticles of a much smaller diameter. As a result, these tiny balls take on the shape of raspberries. Michele Zanini, a doctoral student in Isa's group, was able to alter the surface roughness in a controlled way and create a whole collection of such particles. In a study recently published in Nature Communications, the researchers have demonstrated that they can stabilise both types of emulsion using just one type of these raspberry-shaped particles. This depends solely on the liquid into which the particles are introduced before the emulsion is formed. If the researchers add the particles to the oil phase, a water-in-oil emulsion is formed. Conversely, they are able to stabilise an oil-in-water emulsion (oil droplets finely dispersed in water), if they dissolve their new particles in water first. "These particles can therefore be used as a universal tool for creating emulsions," says Isa.

Coarse particles get stuck earlier

This is because the rough surface reduces the particles' mobility through the droplet's surface, he explains. "Although they push forward on the surface between the liquids, they cannot move as far across it as comparable silica particles with a smooth surface do - the rough particles get stuck before they can reach the energetically most favourable position at the interface," says the ETH professor.

With their raspberry-shaped particles, Isa and his colleagues have laid the foundation for further research in this area, and they have filed a patent for their new process of particle production as emulsion stabilisers.

New applications in sight

There are many possible applications for these particles, namely whenever there is the need to stabilise emulsions; e.g. in the chemical industry. Even though this research was focused on laboratory model systems, the same principles can be extended to the use of naturally occurring rough particles as emulsion stabilisers, to find other potential uses in the food, cosmetics and pharma industry, even though further research is needed in this direction.
-end-


ETH Zurich

Related Water Articles:

Water, water, nowhere
Researchers at the University of Pittsburgh's Swanson School of Engineering have found that the unusual properties of graphane -- a two-dimensional polymer of carbon and hydrogen -- could form a type of anhydrous 'bucket brigade' that transports protons without the need for water, potentially leading to the development of more efficient hydrogen fuel cells for vehicles and other energy systems.
Advantage: Water
When water comes in for a landing on the common catalyst titanium oxide, it splits into hydroxyls just under half the time.
What's really in the water
Through a five-year, $500,000 CAREEER Award from the National Science Foundation, a civil and environmental engineering research group at the University of Pittsburgh's Swanson School of Engineering will be developing new DNA sequencing methods to directly measure viral loads in water and better indicate potential threats to human health.
Jumping water striders know how to avoid breaking of the water surface
When escaping from attacking predators, different water strider species adjust their jump performance to their mass and morphology in order to jump off the water as fast and soon as possible without breaking of the water surface.
Water, water -- the two types of liquid water
There are two types of liquid water, according to research carried out by an international scientific collaboration.
Just add water? New MRI technique shows what drinking water does to your appetite, stomach and brain
Stomach MRI images combined with functional fMRI of the brain activity have provided scientists new insight into how the brain listens to the stomach during eating.
UM researchers found shallow-water corals are not related to their deep-water counterparts
A new study led by scientists at the University of Miami Rosenstiel School of Marine and Atmospheric Science found that shallow-reef corals are more closely related to their shallow-water counterparts over a thousand miles away than they are to deep-water corals on the same reef.
Saline water better than soap and water for cleaning wounds, researchers find
Researchers found that very low water pressure was an acceptable, low-cost alternative for washing out open fractures, and that the reoperation rate was higher in the group that used soap.
UTA research predicting lake levels, moving water to yield better data for water providers
A University of Texas at Arlington environmental engineer is creating an integrated decision support tool for optimal operation of water supply systems that will allow water providers to make better decisions about when to turn on pumps to transfer water from one reservoir system to another and when to release water downstream from the reservoirs.
Surfing water molecules could hold the key to fast and controllable water transport
Scientists at UCL have identified a new and potentially faster way of moving molecules across the surfaces of certain materials.

Related Water Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".