UT Arlington physicists have
developed a new fiber-optic spanner, or wrench, that uses two laser beams to stably
rotate and move microscopic objects, such as living cells, an innovation that
will help scientists to work more efficiently at the microscopic level.
A fiber-optically trapped and
rotated human smooth muscle cell in the center of two transversely offset
fibers. (Photo courtesy S. Mohanty)
The new technology
surpasses current methods of fiber-optic rotation because it allows the object
to be rotated at any axis, giving a fuller view. Through this method, cancer
cells could be imaged during rotation or oocyte cells could be moved during in
vitro fertilization, researchers said. The spanner also can use a “rotating
bead handle” to twist and untwist DNA molecules to allow its sequencing more
rapidly than current methods.
The innovation is detailed in a
new report, “Fiber-optic Spanner,” published today in the journal Optics
Letters and available online (http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-37-24-5030).
Samarendra Mohanty, UT Arlington assistant physics professor, led the research
team and co-authored the paper with doctoral student Bryan Black.
“This technique overcomes many
of the challenges to working with optically trapped microscopic objects and has
numerous possibilities for nanotechnology and biotechnology,” said Mohanty. “It
is widely applicable because it is not limited by the sample’s shape and does
not require any mechanical motion of the fiber. Also, because the tools are
fiber-optic, they can be used at a larger depth inside closed environment such
as the body.”
A research paper, based on
advanced application of this technology, by Black, Mohanty and Dijun Luo, a recent
UT Arlington graduate from the College of Engineering’s Department of Computer
Science, was recently accepted for publication in Applied Physics Letters,
which is published by the American Institute of Physics.
The fiber-optic spanner uses two
laser beams emanating from optic fibers. The fibers are placed on opposite
sides of the object with a transverse offset, or parallel, but not co-linear.
Through a process of counter
propagation, the beams use gradient and scattering forces to trap and rotate an
object. The axis on which the object is rotated can be adjusted by changing the
direction of offset between the two fibers. This gives a fuller, deeper view
than what is available with most existing microscope objective-based laser
tweezers systems, Mohanty said. By adjusting the power of one beam, the object
can also be moved from one place to another. An ultrafast laser beam in one
fiber optic arm can also be used to analyze fluorescence of trapped objects.
“The attention that Dr. Mohanty and his team are receiving for their
work in the lab is well-deserved,” said Carolyn Cason, UT Arlington’s vice
president for research. “His
enhancement of current technology could yield results for a number of fields
and it is a demonstration of the strides that come from determined
Mohanty joined the UT Arlington
College of Science in 2009 and leads the biophysics and physiology group. He is a
co-principal investigator on a $300,000 grant from the Molecular and Cellular
Biosciences division of the National Science Foundation to explore rotational
dynamics of motor proteins.
His research team focuses on
methods to improve the manipulation of microscopic objects by using existing
laboratory tools, such as optical tweezers, and developing their own. They have
published numerous scientific articles, including a December 2011 Nature
Photonics paper that described the use of spinning microparticles to direct the
growth of nerve fiber. (Available online: http://www.nature.com/nphoton/journal/v6/n1/full/nphoton.2011.287.html#/).
The recently developed fiber-optic
spanner also can be used to rotate a micro-motor, or birefringent particle, and
create microfluidic flow. That motion could be used to move objects into a flow
for analyzing or to test variations in viscosity of fluid, Mohanty said. The
method also is translatable to “lab-on-a-chip” devices, tiny devices that
can perform multiple laboratory functions of chemical/physical synthesis or
analysis in parallel. (More information is available here: http://pubs.rsc.org/en/content/articlelanding/2012/LC/c2lc40538e.)
Mohanty is one of several professors
conducting breakthrough optics-related research at UT Arlington, a
comprehensive research institution of more than 33,200 students in the heart of
North Texas. Visit www.uta.edu to learn more.