Featured Research

from universities, journals, and other organizations

Spheres can form squares

Date:
May 23, 2013
Source:
Wageningen University and Research Centre
Summary:
Everybody who has tried to stack oranges in a box knows that a regular packing of spheres in a flat layer naturally leads to a hexagonal pattern, where each sphere is surrounded by six neighbours in a honeycomb-like fashion. Researchers now report an exception to this rule: when small, micrometer-sized particles are placed on a curved oil-water surface, they arrange in a square pattern, as on a chessboard.

Particle organization on oil-water interface of a droplet. The particles are labeled with a fluorescent marker to make them visible.

Everybody who has tried to stack oranges in a box knows that a regular packing of spheres in a flat layer naturally leads to a hexagonal pattern, where each sphere is surrounded by six neighbours in a honeycomb-like fashion. In an article just published on-line in PNAS, researchers from Wageningen University report an exception to this rule: when small, micrometer-sized particles are placed on a curved oil-water surface, they arrange in a square pattern, as on a chessboard.

Since a number of decades, scientists are looking for strategies to create ordered crystal structures of regularly arranged small particles. Such crystals are interesting, because they can be used to control, modulate, or steer visible light in applications like lasers or other optical devices. While creating hexagonal patterns is relatively easy -- this is the natural way in which the particles tend to order -- anything different from that is much more difficult.

The team from the Laboratory of Physical Chemistry and Colloid Science at Wageningen University, part of Wageningen UR, has now found a way to create square particle arrays. To do this, they make use of the surface tension of the underlying oil-water surface, that is the tendency of the surface to minimize its area. When a particle sticks to the liquid surface it deforms the surface somewhat, and thereby increases the total area. The surface tension acts to minimize these deformations, which can be done by clustering all the particles together.

This effect is also responsible for the clumping of breakfast cereals in a bowl of milk or of bubbles at the surface of a soft drink. The researchers have found that this effective attraction between particles resulting from the surface tension depends on how the liquid surface is curved. A slight curving of the surface already makes the interaction between particles highly dependent on their relative orientation, with attraction in two perpendicular directions and repulsion in the other directions. This is what causes the particles to arrange spontaneously in square patterns.

The researchers believe that their findings will lead to new bottom-up strategies for the design of structured materials, to be used in high-tech optical applications.

The research has been supported financially by the Netherlands Organisation for Scientific Research, NWO.


Story Source:

The above story is based on materials provided by Wageningen University and Research Centre. Note: Materials may be edited for content and length.


Journal Reference:

  1. D. Ershov, J. Sprakel, J. Appel, M. A. Cohen Stuart, J. van der Gucht. Capillarity-induced ordering of spherical colloids on an interface with anisotropic curvature. Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1222196110

Cite This Page:

Wageningen University and Research Centre. "Spheres can form squares." ScienceDaily. ScienceDaily, 23 May 2013. <www.sciencedaily.com/releases/2013/05/130523093147.htm>.
Wageningen University and Research Centre. (2013, May 23). Spheres can form squares. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2013/05/130523093147.htm
Wageningen University and Research Centre. "Spheres can form squares." ScienceDaily. www.sciencedaily.com/releases/2013/05/130523093147.htm (accessed July 30, 2014).

Share This




More Matter & Energy News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
China's Drone King Says the Revolution Depends on Regulators

China's Drone King Says the Revolution Depends on Regulators

Reuters - Business Video Online (July 30, 2014) Comparing his current crop of drones to early personal computers, DJI founder Frank Wang says the industry is poised for a growth surge - assuming regulators in more markets clear it for takeoff. Jon Gordon reports. Video provided by Reuters
Powered by NewsLook.com
3Doodler Bring 3-D Printing to Your Hand

3Doodler Bring 3-D Printing to Your Hand

AP (July 30, 2014) 3-D printing is a cool technology, but it's not exactly a hands-on way to make things. Enter the 3Doodler: the pen that turns you into the 3-D printer. AP technology writer Peter Svensson takes a closer look. (July 30) Video provided by AP
Powered by NewsLook.com
Climate Change Could Cost Billions, According To White House

Climate Change Could Cost Billions, According To White House

Newsy (July 29, 2014) A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins