Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Less is more: Study of tiny droplets could have big applications

Under a microscope, a tiny droplet slides between two fine hairs like a roller coaster on a set of rails until — poof — it suddenly spreads along them, a droplet no more.
That instant of change, like the popping of soap bubble, comes so suddenly that it seems almost magical. But describing it, and mapping out how droplets stretch into tiny columns, is a key to understanding how liquids affect fibrous materials from air filters to human hair. And that knowledge allows scientists to better describe why water soaks into some materials, beads atop others and leaves others matted and clumped.

To get those answers, an international team of researchers led by scientists at Princeton University made a series of close observations of how liquid spreads along flexible fibers. They were able to construct a set of rules that govern the spreading behavior, including some unexpected results. In a paper published Feb. 23 in Nature, the researchers found that a key parameter was the size of the liquid drop.

"That surprised us," said Camille Duprat, the paper's lead author. "No one had thought about volume very much before."

Duprat, a postdoctoral researcher in the Department of Mechanical and Aerospace Engineering, said the research team was able to determine drop sizes that maximized wetting along certain fibers, which could allow for increased efficiency in industrial applications of liquids interacting with fibrous materials — from cleaning oil slicks to developing microscopic electronics. The team also discovered a critical drop size above which the drop would not spread along the fibers, but would remain perched like a stranded roller coaster car.

"If in any engineering problem you can learn an optimal size above which something does not happen, you have learned something very important about the system," said Howard Stone, a co-author of the paper.

A study led by researchers at Princeton University has yielded insights into how liquid spreads along flexible fibers, which could allow for increased efficiency in various industrial applications. The team's experiments show that the size of oil droplets determines whether they spread along flexible glass fibers. At the critical size (top two examples), the droplets expand into columns of liquid, but larger droplets sit immobile between the glass rods (bottom example). (Image courtesy of Camille Duprat and Suzie Protière)

Stone, the Donald R. Dixon '69 and Elizabeth W. Dixon Professor in Mechanical and Aerospace Engineering, said the team conducted a series of experiments observing how liquid spread along different types of fibers. The plan was to make broad observations and derive a governing theory from the experiments.

"We had a lot of results and at some point we started having these meetings trying to understand what we had," he said. "We realized the way to think about it was in the way of critical sizes."

Besides Duprat and Stone, the researchers included Alexander Beebe, a Princeton junior majoring in mechanical and aerospace engineering, and Suzie Protière, an associate scientist at the University of Pierre and Marie Curie in Paris. The research at Princeton was conducted with support from Unilever.

The researchers determined that the critical parameters governing how drops interact with flexible fibers were the size of the droplet, the flexibility and radii of the fibers, and the geometry of the fiber array (such as the space and angle between pairs of fibers).

The experiment examined the behavior of a droplet placed on a pair of flexible glass fibers that was clamped at one end and free at the other. When the drop was placed at the clamped end of the pair, the fibers bent inward and the drop moved toward the free end. As the drop moved further out, the fibers bent more, and the drop accelerated and elongated. At some point, the drop spontaneously spread and formed a liquid column between the now-coalesced fibers.

To understand the critical drop size at which no spreading occurred, the researchers measured the distance between the fibers at the instant that the spreading began. They concluded that spreading occurs when the spacing between the fibers dictates that it takes less energy for the liquid to form a column than it does to remain as a drop. The researchers were also able to use their observations to calculate an optimal drop size that resulted in a maximum spread of liquid along the fibers.

The researchers said their findings could have a wide array of applications. Waterfowls' feathers, for example, are a natural array of fibers that keep the birds warm and dry. When oil coats the feathers, it disrupts the fiber arrangement by clumping the feathers. Using goose feathers, the team found that oil droplets above a certain size did not spread along the fibers and allowed the feather to be cleaned more easily. Duprat said the findings could have implications for methods used to rescue injured birds and also for dispersants applied to oil slicks after accidents.

On the other hand, items such as aerosol-removal filters or hairsprays require total spreading along fibers for effectiveness. The control of droplet sizes could also prove important for the fabrication of microstructures by resulting in the optimal spread of liquid material along pillars and similar forms, such as those found in various forms of lithography used in micro- and nanofabrication.

"Materials react differently to different drop sizes," Duprat said. "You can design a material to react to a specific drop size or you can produce a drop size to affect a specific material."

John Sullivan | EurekAlert!
Further information:

More articles from Materials Sciences:

nachricht From ancient fossils to future cars
21.10.2016 | University of California - Riverside

nachricht Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

New method increases energy density in lithium batteries

24.10.2016 | Power and Electrical Engineering

International team discovers novel Alzheimer's disease risk gene among Icelanders

24.10.2016 | Life Sciences

New bacteria groups, and stunning diversity, discovered underground

24.10.2016 | Life Sciences

More VideoLinks >>>