Nav: Home

'Dancing' holes in droplets submerged in water-ethanol mixtures

June 30, 2018

Tokyo, Japan - Researchers from Tokyo Metropolitan University have observed the formation of holes that move by themselves in droplets of ionic liquids (IL) sitting inside water-ethanol mixtures. This curious, complex phenomenon is driven by an interplay between how ionic liquids dissolve, and how the boundary around the droplet fluctuates. Self-driven motion is a key feature of active matter, materials that use ambient energy to self-propel, with potential applications to drug delivery and nano-machine propulsion.

Most people are familiar with how things mix or dissolve. For example, we know that water and ethanol mix very well at room temperature; take alcoholic beverages. How well they mix depends on the environment the mixture is in, like temperature and pressure.

However, dissolution takes a complex turn when we add another component. A team led by Associate Professor Rei Kurita, Department of Physics, Tokyo Metropolitan University, were studying how an ionic liquid (IL) dissolved in a mixture of water and ethanol. Ionic liquids are liquids composed entirely of ions in ambient conditions; properties like their resistance to drying and ability to dissolve otherwise difficult materials have led to their being referred to as a "solvent of the future" [1], with a focus on how they might play a role in industrial processes e.g. battery production, pharmaceuticals, and recycling.

The team placed a small droplet of IL at the bottom of a mixture of ethanol and water. With the temperature and particular ratio of ethanol to water they used, they expected a boundary or interface to form between the IL and the water-ethanol above it, and for the two to mix gradually. Yet, what they saw was startling: over time, holes emerged inside the IL droplet, and the holes could propel themselves inside the droplet.

They found that this curious phenomenon was the result of how the composition of the water-ethanol mixture naturally fluctuated around the interface. The conditions were such that the mixture is close to a critical point, where small variations in composition can have major consequences. In this case, they were enough to locally promote mixing of the IL into the water-ethanol mixture; the unique way in which ILs interact with water led to even further local changes in composition, leading to a positive feedback loop, or instability. The effect was so drastic that they led to variations in the surface tension, driving the surface to become spontaneously bumpy, form holes, and generate the large flows required to move them around. These holes have been dubbed active holes.

Their discovery paves the way for a broad new class of synthetic active matter, materials that can spontaneously take energy from its surroundings and convert it into motion. With possible applications to drug delivery and propulsion at the nanometer scale, this new phenomenon might inspire investigations into novel industrial uses as well as further accelerate academic interest in active phenomena.
-end-
This work was supported by a JSPS KAKENHI Grant-in-Aid for Scientific Research (B) (17H02945), Scientific Research into Innovative Areas (16K13865) and for Young Scientists (17K14356). The study has been published online in the journal Soft Matter and selected for the back cover of the issue (28 June 2018, Issue 24).

[1] R D Rodgers and K R Seddon, 2003, Science, 302, 5646, 792-793 Issue 24, 2018

Tokyo Metropolitan University

Related Ethanol Articles:

Discovery could lead to sustainable ethanol made from carbon dioxide
A recent discovery by Stanford University scientists could lead to a new, more sustainable way to make ethanol without corn or other crops.
Scientists engineer sugarcane to produce biodiesel, more sugar for ethanol
A multi-institutional team led by the University of Illinois have proven sugarcane can be genetically engineered to produce oil in its leaves and stems for biodiesel production.
Nano-spike catalysts convert carbon dioxide directly into ethanol
In a new twist to waste-to-fuel technology, scientists have developed an electrochemical process that uses tiny spikes of carbon and copper to turn carbon dioxide, a greenhouse gas, into ethanol.
A more efficient way of converting ethanol to a better alternative fuel
A research team at the University of Rochester has developed a series of reactions that results in the selective conversion of ethanol to butanol, without producing unwanted byproducts.
Ethanol refining may release more of some pollutants than previously thought
Ethanol fuel refineries could be releasing much larger amounts of some ozone-forming compounds into the atmosphere than current assessments suggest, a new study finds.
Ethanol and heterogeneous catalysts for biodiesel production
Biodiesel is an alternative fuel to conventional fossil ones. The EU policies of boosting biodiesel have achieved its implementation in the transport fuels market and increasingly its sustainable nature is being taken into account.
Thermotolerant yeast can provide more climate-smart ethanol
With a simple mutation, yeast can grow in higher than normal temperatures.
Ethanol fireplaces: The underestimated risk
Ethanol fireplaces are becoming more and more popular. However, they are not only highly combustible -- in the past, severe accents have occurred repeatedly with decorative fireplaces.
Ozone levels drop 20 percent with switch from ethanol to gasoline
A Northwestern University study by an economist and a chemist reports that when fuel prices drove residents of Sao Paulo, Brazil, to mostly switch from ethanol to gasoline in their flexible-fuel vehicles, local ozone levels dropped 20 percent.
Stanford scientists discover a novel way to make ethanol without corn or other plants
Stanford scientists have created a copper-based catalyst that produces large quantities of ethanol from carbon monoxide gas at room temperature.

Related Ethanol 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

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...