Nav: Home

UMass Amherst physicists speed up droplet-wrapping process

February 15, 2018

AMHERST, Mass. - Experimental physicists at the University of Massachusetts Amherst today report that they have developed a fast, dynamic new process for wrapping liquid droplets in ultrathin polymer sheets, so what once was a painstaking process taking tens of minutes can now be done in a fraction of a second.

Physics professor Narayanan Menon, with current postdoctoral researcher Deepak Kumar, former postdoc Joseph Paulsen and professor of polymer science Thomas Russell, report their findings in the current issue of Science. Paulsen is now at Syracuse University.

As Menon explains, many research groups around the world are working on the problem of wrapping liquid droplets to stabilize emulsions, which can be useful in drug delivery systems, for example, or for remediating oil spills.

The customary method is to use a layer of fluid that acts as a surfactant to keep oils and water in suspension. Mayonnaise is an emulsion of oil and water, Menon notes, with egg white as the surfactant that holds it in suspension. But a liquid surfactant layer has no rigidity, it cannot hold a shape. The UMass Amherst researchers were looking for a wrap with a finite rigidity.

He says, "Let's say I ask you to wrap up a basketball and I give you tape and paper. You do the best you can, but it's not going to come out very neatly. It will have gaps and overlaps. With our new process, you throw the basketball at the paper, and it comes out perfectly wrapped."

Menon adds, "If you're thinking of doing this sort of wrapping over and over, speed and ease of use make all the difference. The quick and simple solution Kumar has found is a huge advance, and once he mastered it and identified the most important parameters, he found he could get adventurous and make different shapes. We show that we have made cubes and a tetrahedron, for example."

Also, "The materials are common polymers and common liquids, just oil and water. No magic ingredients needed, and we can go freely from oil droplets in water and vice versa. The seams are held in place by the dislike of the fluid inside for the fluid outside, so the wrapping edges meet right at the seam and there is no overlap and no gap."

Kumar, first author of the paper, points out that the new technique exploits the fast dynamics of droplet impact to achieve wrapping of oil droplets by ultrathin polymer films in a water phase. "Despite the violence of splashing events, the process robustly yields wrappings that are optimally shaped to maximize the enclosed fluid volume and have near-perfect seams," he and colleagues write. "We achieve wrappings of targeted three-dimensional shapes by tailoring the two-dimensional boundary of the films and show the generality of the technique by producing both oil-in-water and water-in-oil wrappings."

Important factors involved in the practical success of the new method, Kumar notes, are droplet fluid density and the size of the droplet in relation to the size of the thin polymer sheet. Menon quips, "It doesn't work if you throw a basketball at a bed sheet, nor at a postage stamp. The size of the droplet and the sheet must be related."

An unexpected bonus of this work, the authors point out, is that they have achieved not only the practical success, but they were able to answer part of the deeper scientific question of mechanism. Kumar says, "We propose some ideas, but we don't have the answer to all the questions."

Menon says he hopes experimental physicists who read about this work will quickly grasp that "it's technically easy and you should go do it for yourself. In fact, you should take it and go in directions that we haven't thought about. We hope other researchers will think of more and different applications than we would by ourselves. If you want to add complexity, you could put a layer or a pattern on the inside of the wrapping, or you could add a window to make it slightly leaky. Once you know how to do the technique, it's not fussy."
This work was supported by the W.M. Keck Foundation and the National Science Foundation.

University of Massachusetts at Amherst

Related Water Articles:

Source water key to bacterial water safety in remote Northern Australia
In the wet-dry topics of Australia, drinking water in remote communities is often sourced from groundwater bores.
Our water cycle diagrams give a false sense of water security
Pictures of the earth's water cycle used in education and research throughout the world are in urgent need of updating to show the effects of human interference, according to new analysis by an international team of hydrology experts.
Water management helped by mathematical model of fresh water lenses
In this paper, the homeostasis of water lenses was explained as an intricate interaction of the following physical factors: infiltration to the lens from occasional (sporadic) rains, permanent evaporation from the water table, buoyancy due to a density contrast of the fresh and saline water, and the force of resistance to water motion from the dune sand.
The age of water
Groundwater in Egypt's aquifers may be as much as 200,000 years old and that's important to know as officials in that country seek to increasing the use of groundwater, especially in the Eastern Desert, to mitigate growing water stress and allow for agricultural projects.
Water that never freezes
Can water reach minus 263 degrees Celsius without turning into ice?
Peanuts that do more with less water
Researchers are studying peanut varieties to find a 'water conservation' trait.
Molecular adlayer produced by dissolving water-insoluble nanographene in water
Even though nanographene is insoluble in water and organic solvents, Kumamoto University and Tokyo Institute of Technology researchers have found a way to dissolve it in water.
Water-worlds are common: Exoplanets may contain vast amounts of water
Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth.
Artificial intelligence saves water for water users associations
A research group at the University of Cordoba has developed a model based on artificial intelligence techniques that can predict how much water each water user will use.
In desert trials, next-generation water harvester delivers fresh water from air
UC Berkeley scientists who last year built a prototype harvester to extract water from the air using only the power of the sun have scaled up the device to see how much water they can capture in arid conditions in Arizona.
More Water News and Water Current Events

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

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.