WEST LAFAYETTE, Ind. - 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 a
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