Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Solution to beading-saliva mystery has practical purposes

10.06.2010
Researchers have discovered precisely why strands of some fluids containing long molecules called polymers form beads when stretched, findings that could be used to improve industrial processes and for administering drugs in "personalized medicine."

"Any kindergartner is familiar with this beading phenomenon, which you can demonstrate by stretching a glob of saliva between your thumb and forefinger," said Osman Basaran, Purdue's Burton and Kathryn Gedge Professor of Chemical Engineering.

Before the strand of spittle breaks, a string of beads is formed.

"The question is, why does this beading take place only in some fluids containing polymers but not others?" Basaran said.

Now engineers and scientists at Purdue, the Massachusetts Institute of Technology and Rice University have solved the riddle in work led by Purdue postdoctoral researcher Pradeep Bhat. The researchers have determined the mechanism behind the beading and created a computational model to simulate the phenomenon.

Knowing the answer to this question might enable researchers to design systems that precisely control bead formation, leading to improvements in various technologies such as inkjet printing. The information also might be used in a system that precisely dispenses the correct dose of medications for individual patients based on simple blood tests.

Findings are detailed in a paper published online this week in the journal Nature Physics. The paper was written by Bhat; Purdue graduate student Santosh Appathurai; Michael T. Harris, a Purdue professor of chemical engineering; Matteo Pasquali, a professor in chemical and biomolecular engineering at Rice; Gareth H. McKinley, a professor of mechanical engineering at MIT; and Basaran.

Saliva and other complex "viscoelastic" fluids like shaving cream and shampoo contain long chains of molecules called polymers. In the case of saliva, the polymers are proteins known as mucopolysaccharides. In comparison, liquids such as water and other so-called "Newtonian" fluids do not form the beads because they lack polymers.

Conventional wisdom has held that all fluids containing polymers should form the beads, but researchers have shown that assumption to be wrong and have demonstrated why.

The researchers tested saliva and a material contained in a strip on the leading edge of disposable razors.

"You moisten the razor strip with water, which causes it to swell, press it against a finger and pull it," Basaran said. "Unlike saliva, you see strands of liquids formed but no beads."

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 bead formation depends on two ratios: the viscous force compared to inertial force and the relaxation time compared to the capillary time.

Because smearing "satellite" beads form around droplets produced by an inkjet printer, learning how to control bead formation might be used to improve printing. Findings also may help to improve an industrial process called electrospinning, used to make a variety of products, and spray coating used in painting.

"The idea is that, if you are operating an inkjet printer, for example, you would be able to control these ratios to prevent the bead formation," Basaran said.

Findings may help to perfect a new type of drug-dispensing technology being developed for "personalized medicine" through an Engineering Research Center for Structured Organic Particulate Systems, funded by the National Science Foundation and made up of researchers from Purdue, Rutgers University, the New Jersey Institute of Technology and the University of Puerto Rico.

The technique involves using an inkjet-printing nozzle to deposit drops of medication onto an edible substrate, such as paper or a sugar pill. The approach might be used by patients with disorders that require precise doses of medication depending on daily blood measurements.

"Patients might be able to do this even at home," said Basaran, whose research, carried out in collaboration with Harris, is affiliated with the NSF-funded center. "The patient will perform a routine sort of blood analysis, similar to blood-glucose monitoring, and then use this device to 'print' the exact quantity of drug based on the blood measurement, which would be done every day."

Writer: Emil Venere, (765) 494-4709, venere@purdue.edu
Sources: Osman Basaran, (765) 494-4061, obasaran@purdue.edu
Pradeep Bhat, pbhat@purdue.edu

Emil Venere | EurekAlert!
Further information:
http://www.purdue.edu

More articles from Physics and Astronomy:

nachricht Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>