A UT Arlington engineering professor has proven that the effect of mass is important, can be measured and has a significant impact on any calculations and measurements at the sub-micrometer scale.
The findings help to better understand movement of nano-sized objects in fluid environments that can be characterized by a low Reynolds number, which often occurs in biological systems. The unconventional results are consistent with Newton’s Second Law of Motion, a well-established law of physics, and imply that mass should be included in the dynamic model of these nano-systems. The most widely accepted models omit mass at that scale.
Alan Bowling, assistant professor of mechanical and aerospace engineering
Alan Bowling, an assistant professor of mechanical and aerospace engineering,
collaborated with Samarendra Mohanty, an assistant physics professor, and
doctoral students Mahdi Haghshenas-Jaryani, Bryan Black and Sarvenaz Ghaffari,
as well as graduate student James Drake to make the discovery.
A key advantage of the new model is that it can be used to build
computer simulations of nano-sized objects that have drastically reduced
run times as compared to a conventional model based on Newton’s second law.
These conventional models have run times of days, weeks, months and years while
the new model requires only seconds or minutes to run.
In the past, researchers attempted to address the long run time by
omitting the mass terms in the model. This resulted in faster run times but,
paradoxically, violated Newton’s second law upon which the conventional model
was based. The remedy for this paradox was to argue that mass was unimportant
at the nano-scale.
However, the new model retains mass, and predicts unexpected
motion of nano-sized objects in a fluid that has been experimentally observed.
The new model also runs much faster than both the conventional and massless
It is expected that this new model will significantly accelerate
research involving small-scale phenomena.
Research areas that Bowling and collaborators at UT Arlington are
currently investigating include cell migration, protein function, bionic
medical devices and nanoparticle suspensions for storing thermal energy.
However, the applications for the computer simulation in medicine, biology, and
other fields are endless.
The research is detailed in the paper “Dynamics
of Microscopic Objects in Optical Tweezers: Experimental Determination of
Underdamped Regime and Numerical Simulation using Multiscale Analysis” and
published online by the Journal of Non-Linear Dynamics. The
paper is scheduled for publication in the journal’s print version later this
Khosrow Behbehani, dean of the College of Engineering,
said the team’s findings may alter ways of thinking throughout the engineering
and scientific worlds.
“The paper is only the beginning for this research,” Behbehani
said. “I anticipate a high level of interest in the findings. It could
transform the way we conduct research in nano-engineering by providing
researchers with the ability to study such physical phenomena at such small
scale through the model.”
The team used optical tweezers previously developed by Mohanty to
measure oscillations that occur at the nano scale, thus proving that mass and
acceleration must be considered at that level as well.
“We proved it in the lab,” Bowling said. “Publication in an
accepted journal is the next step in gaining mass acceptance of the idea, which
flies in the face of what most people believe now.”
The discovery resulted from a 2012 National Science Foundation grant
project in which the UT Arlington team investigated a new model for
how motor proteins behave in the body. The NSF award was funded through the
Early Concept Grants for Exploratory Research, or EAGER program. The grants
support exploratory work in its early stages on untested, but potentially
transformative, research ideas or approaches.
The University of Texas at Arlington is a comprehensive research
institution of more than 33,300 students and 2,300 faculty members in the
epicenter of North Texas. It is the second largest institution in the
University of Texas System. Research expenditures reached almost $78 million
last year. Visit www.uta.edu for more