Navigation Links
Answer to saliva mystery has practical impact
Date:6/11/2010

Researchers at Rice University, Purdue University and the Massachusetts Institute of Technology have solved a long-standing mystery about why some fluids containing polymers -- including saliva -- form beads when they are stretched and others do not.

The findings are published online this week in the journal Nature Physics.

Study co-author Matteo Pasquali, professor in chemical and biomolecular engineering at Rice, said the study answers fundamental scientific questions and could ultimately lead to improvements as diverse as ink-jet printing, nanomaterial fiber spinning and drug dispensers for "personalized medicine."

Co-author Osman Basaran, Purdue's Burton and Kathryn Gedge Professor of Chemical Engineering, said, "Any kindergartner is familiar with this beading phenomenon, which you can demonstrate by stretching a glob of saliva between your thumb and forefinger. The question is, 'Why does this beading take place only in some fluids containing polymers but not others?'"

Pasquali said, "In answering the question about why some fluids do this and others do not, we are addressing everyday processes that apply to fiber and droplet formation, not just in multibillion-dollar industrial plants but also in fluids produced in living cells."

Saliva and other complex "viscoelastic" fluids like shaving cream and shampoo contain long molecules called polymers. When a strand of viscoelastic fluid is stretched, these polymers can cause a line of beads to form just before the strand breaks.

Pasquali said the explanation for why some viscoelastic fluids form beads and others do not was decades in the making. The origins of the work can be traced to Pasquali's and Basaran's doctoral research adviser, L.E. "Skip" Scriven of the University of Minnesota. Pasquali said Scriven worked out the basics of the competition between capillary, inertial and viscous forces in flows during the 1970s and 1980s. In the mid-1990s, during his doctoral research at Minnesota, Pasquali expanded on Scriven's earlier work to include the effects of viscoelasticity, which originates in liquid microstructures and nanostructures. Finally, Pasquali's former doctoral student, Pradeep Bhat, the lead author of the new study, took up the mantle nine years ago as a Ph.D. student in Pasquali's lab and continued working on the problem for the past three years as a postdoctoral researcher in Basaran's lab at Purdue.

Bhat, Basaran and Pasquali found that a key factor in the beading mechanism is fluid inertia, or the tendency of a fluid to keep moving unless acted upon by an external force.

Other major elements are a fluid's viscosity; the time it takes a stretched polymer molecule to "relax," or snap back to its original shape when stretching is stopped; and the "capillary time," or how long it would take for the surface of the fluid strand to vibrate if plucked.

"It turns out that the inertia has to be large enough and the relaxation time has to be small enough to form beads," Bhat said.

The researchers discovered that bead formation depends on two ratios: the viscous force compared with inertial force and the relaxation time compared with the capillary time.


'/>"/>

Contact: David Ruth
druth@rice.edu
713-348-6327
Rice University
Source:Eurekalert

Related biology news :

1. Microbes answer more questions collectively
2. U of I researchers say foliar fungicides may not be the answer for hail-damaged corn
3. Microbial answer to plastic pollution?
4. An answer to another of lifes big questions
5. Bubble physicist counts bubbles in the ocean to answer questions about climate, sound, light
6. Studying hair of ancient Peruvians answers questions about stress
7. Are sterile mosquitoes the answer to malaria elimination?
8. Avoiding dangerous climate change: Is geo-engineering the answer?
9. Critical Zone Observatory seeks to answer climate change questions
10. All tied up: Tethered protein provides long-sought answer
11. Researcher looks for answers about unique disease-resistant gene
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/11/2017)... April 11, 2017 NXT-ID, Inc. (NASDAQ: ... company, announces the appointment of independent Directors Mr. Robin ... its Board of Directors, furthering the company,s corporate governance and ... Gino Pereira ... look forward to their guidance and benefiting from their considerable ...
(Date:4/5/2017)... 4, 2017 KEY FINDINGS The ... at a CAGR of 25.76% during the forecast period ... primary factor for the growth of the stem cell ... MARKET INSIGHTS The global stem cell market ... and geography. The stem cell market of the product ...
(Date:3/30/2017)... HONG KONG , March 30, 2017 ... developed a system for three-dimensional (3D) fingerprint identification by adopting ground ... technology into a new realm of speed and accuracy for use ... applications at an affordable cost. ... ...
Breaking Biology News(10 mins):
(Date:6/19/2017)... , ... June 19, 2017 , ... ... for clinical development reported today that it is launching two new additions of ... will be demonstrating new capabilities at the DIA 2017 Annual Meeting in Chicago, ...
(Date:6/16/2017)... ... 2017 , ... Cognition Corporation , a software company ... of its “From the Helm” Webinar Series. , The next two free ... design control exercises. Led by David Cronin, Cognition’s CEO, the half-hour public webinars ...
(Date:6/15/2017)... ... 2017 , ... New resistant soybean and cotton cropping systems ... amaranth and other broadleaf weeds resistant to glyphosate. But scientists with the Weed ... known to drift and to cause harm to sensitive, off-target broadleaf plants. , ...
(Date:6/15/2017)... (PRWEB) , ... June 15, 2017 , ... ... Saranas, a promising new medical device startup. Dan Parsley, angelMD’s SVP of Corporate ... angelMD members, and this angelMD syndicate is part of Saranas’ recently announced $4 ...
Breaking Biology Technology: