Stirred, not shaken: Physicists gain more particle control

Mar 22, 2013 by Blaine Friedlander

Cornell physicists can now precisely control how particles in viscous liquids swirl, twirl and whirl. Think of coffee and adding cream—and gaining control of the particles in the cream. Understanding this concept could allow chemists, physicists and engineers to better detect molecules, control the mixture of nanoscale particles and enhance self-assembly in solutions.

Brian Leahy, Cornell doctoral student in the field of physics, presented "Revisiting Taylor Dispersion: Differential Enhancement of Rotational and Translational Diffusion Under Oscillatory Shear" at the American Physical Society meeting, Baltimore, March 18. His co-researchers include: Xiang Cheng, physics postdoctoral researcher; Itai Cohen, professor of physics; and Desmond Ong '11.

If you stir, diffusion—the random jostling of small particles from —is enhanced. This enhancement is called Taylor dispersion. "Stirring transports the cream through the coffee and also enhances diffusion of the cream particles," said Leahy.

Using 3-D imaging microscopes, the physicists can now also see the orientation of oblong particles in a , providing the ability to measure the individual particle for the first time.

"By adding shear and adjusting the flow, particles can not only be oriented but their rotational diffusion can also change," said Leahy.

In a fluid, oblong particles that are small enough can change their orientation due to rotational diffusion that arises when fluid molecules kick the particles in random directions. When the particle-laden fluid is rubbed between two oscillating plates, the oblong particles also rotate end-on-end in what is known as a Jeffery's .

The researchers showed that the combination of rotational diffusion and Jeffery orbits has an effect that is bigger than the so-called "sum of the parts," so that the particles change their orientation faster than either mechanism alone.

While this is basic, physical research, understanding these concepts could lead to opportunities in other fields, said Cohen: improved self-assembly of specially shaped particles, designer materials, or producing liquids with directional dependence that flow easily.

Explore further: Missing link in metal physics explains Earth's magnetic field

add to favorites email to friend print save as pdf

Related Stories

Researchers track nanoparticle dynamics in three dimensions

Aug 03, 2012

(Phys.org) -- Researchers from the NIST Center for Nanoscale Science and Technology have used three-dimensional single-particle tracking to measure the dynamic behavior of individual nanoparticles adsorbed at the surface ...

Researchers create 'handshaking' particles

Mar 24, 2010

Physicists at New York University have created "handshaking" particles that link together based on their shape rather than randomly. Their work, reported in the latest issue of the journal Nature, marks the first time scient ...

Physicists undo the 'coffee ring effect' (w/ video)

Aug 17, 2011

A team of University of Pennsylvania physicists has shown how to disrupt the "coffee ring effect" — the ring-shaped stain of particles leftover after coffee drops evaporate — by changing the particle ...

Physicists shine a light on particle assembly (w/ video)

Jan 31, 2013

New York University physicists have developed a method for moving microscopic particles with the flick of a light switch. Their work, reported in the journal Science, relies on a blue light to prompt colloids to move and th ...

Recommended for you

Particle physicists discuss JUNO neutrino experiment

17 hours ago

The construction of the facilities for the JUNO neutrino experiment has been initiated with an official groundbreaking ceremony near the south Chinese city of Jiangmen. Involved in the Jiangmen Underground ...

New pathway to valleytronics

Jan 27, 2015

A potential avenue to quantum computing currently generating quite the buzz in the high-tech industry is "valleytronics," in which information is coded based on the wavelike motion of electrons moving through ...

New portable vacuum standard

Jan 26, 2015

A novel Portable Vacuum Standard (PVS) has been added to the roster of NIST's Standard Reference Instruments (SRI). It is now available for purchase as part of NIST's ongoing commitment to disseminate measurement ...

Prototype for first traceable PET-MR phantom

Jan 26, 2015

As cancer diagnostic tools, a new class of imagers – which combines positron-emission tomography (PET) with magnetic resonance imaging (MR or MRI) – has shown promise in the few years since these hybrid ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.