Navigation Links
NJIT engineer discovers why particles disperse on liquids
Date:11/17/2009

Even if you are not a cook, you might have wondered why a pinch of flour (or any small particles) thrown into a bowl of water will disperse in a dramatic fashion, radiating outward as if it was exploding. Pushpendra Singh, PhD, a mechanical engineering professor at NJIT who has studied and written about the phenomenon, has not only thought about it, but can explain why.

He says that what's known as the "repulsive hydrodynamic force arising from the oscillation of particles" causes them to disperse. A particle trapped in a liquid surface vibrates up and down from its equilibrium position on the surface, or interface, where air meets water. When many particles do this simultaneously, an explosive dispersion occurs.

"Spontaneous Dispersion of Particles on Liquid Surfaces," which appeared in the Nov. 11, 2009 early edition of the Proceedings of the National Academy of Sciences explains the theory. The National Science Foundation has supported this research.

Singh says that when small particles, such as flour or pollen, come in contact with a liquid surface, they immediately disperse and form a monolayer. The dispersion occurs so quickly that it appears explosive, especially on the surface of liquids like water.

This explosive dispersion is a consequence of the capillary force pulling particles towards their equilibrium positions in the interface. The capillary force causes the particles to accelerate very rapidly.

"If a particle barely touches the interface, it is pulled onto the surface," said Singh. "For example, if the contact angle for a spherical particle is 90 degrees, it floats in the state of equilibrium so that one-half of it is above the surface and the remaining half is below. If the particle, however, is not in this position, the capillary force will force it to be."

What's interesting is that the smaller the particles, the faster they move. For nanometer-sized particles like viruses and proteins, the velocity or speed on an air-water interface can be as high as 167 kilometers (about 100 miles) per hour.

Singh says the motion of the particles is dominated by inertia because the viscous dampingwhich is like frictionis too small. He compares the situation to a moving pendulum. "The pendulum will oscillate many times before friction makes it stop," he says. "If friction is too great, it won't oscillate."

Eventually, the particles which have been oscillating around their equilibrium point will stop--thanks to viscous drag which causes resistance to the motion.

"Let me explain more about viscous drag," said Singh. "When a body, such as a ball, moves through air or liquid, it will resist the motion. This resistance is caused by viscous drag. Or look at it this way. When a particle is adsorbed at a surface, it acquires a part of the released interfacial energy as kinetic energy," he says. "The particle dissipates this kinetic energy by oscillating from its equilibrium height in the interface. The act gives rise to repulsive hydrodynamic forces, the underlying cause of why particles disperse."


'/>"/>

Contact: Sheryl Weinstein
Sheryl.m.weinstein@njit.edu
973-596-3436
New Jersey Institute of Technology
Source:Eurekalert  

Related biology news :

1. Avoiding dangerous climate change: Is geo-engineering the answer?
2. Genencor Wins The American Institute of Chemical Engineers (AIChE) Sustainable Energy Award For Accellerase(R) Cellulosic Ethanol Enzymes
3. Engineering Careers for the Next Generation, Nov. 18
4. Battling cancer with engineering: NCI funds new $13 million cancer research center led by Cornell
5. Clemson bioengineer uses nanoparticles to target drugs
6. CHEO RI study uses sophisticated genetic engineering to improve insulin-producing beta cells
7. Louisiana Tech University receives grant to advance women in engineering, science
8. Yale engineers track bacterias kayak paddle-like motion for first time
9. Siebel Foundation awards top UC San Diego bioengineering graduate students
10. Boston University engineer to use $2.5 million NIH grant to cells reaction to physical force
11. Sakayu Shimizu of Kyoto University recipient of 2009 Enzyme Engineering Award
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
NJIT engineer discovers why particles disperse on liquids
(Date:11/22/2016)... MINNETONKA, Minn. , Nov. 22, 2016   ... that supports the entire spectrum of clinical research, is ... by Medical LiveWire Healthcare and Life Sciences Awards ... This award caps off an unprecedented year of recognition ... clinical trials for over 15 years. iMedNet ...
(Date:11/17/2016)... 2016  AIC announces that it has just released a new white paper authored ... scale-out plus high speed data transfer storage solutions. Photo - http://photos.prnewswire.com/prnh/20161116/440463 ... ... ... Setting up a high performance computing or HPC system ...
(Date:11/14/2016)...  xG Technology, Inc. ("xG" or the "Company") (Nasdaq: ... for use in challenging operating environments, announced its results ... will hold a conference call to discuss these results ... (details below). Key Recent Accomplishments ... agreement to acquire Vislink Communication Systems. The purchase is ...
Breaking Biology News(10 mins):
(Date:12/9/2016)... ... 09, 2016 , ... There’s a winning streak at Voxx Analytics: the tech ... after winning the award last year as well. Employees nominate their companies for the ... Vesely pointed to the tech company’s upbeat environment as a reason. “We don’t answer ...
(Date:12/9/2016)... ... ... Aditya Humad, Acting CFO of AxioMed and Managing Partner of KICVentures, is pleased ... now gaining interest from Silicon Valley. “It was satisfying to complete the due diligence ... that, “We expect interest to continue to rise as AxioMed completes its cleanroom assembly ...
(Date:12/9/2016)... , Dec. 9, 2016  A platform of ... are moving one step closer to becoming viable ... OrthoMend Research, Inc., a start-up company from ... exclusive license for these novel absorbable bone fixation ... them for commercial use. The company has leased ...
(Date:12/9/2016)... , Dec. 9, 2016 /PRNewswire/ - Portage Biotech ... Exchange: PBT.U), is pleased to announce that Biohaven has ... New Haven, Connecticut (PRWEB) Dec 9, ... or "Biohaven") announced today that the U.S. Food and ... designation request covering its drug candidate BHV-0223, an orally ...
Breaking Biology Technology: