New technique to trap and move tiny particles using laser

Education, Engineering, Science, Research,

New Delhi, October 02. (By Sunderarajan Padmanabhan): In a development that could help make advanced lab-on-chip devices like portable diagnostic kits, researchers at the Centre for Nano Science and Engineering (CeNSE) in Indian Institute of Science, Bengaluru, have come up with a technique to trap and move nano-sized particles in a fluidic medium using light.

Technique is developed by
PhD student

The technique, developed
by PhD student Souvik Ghosh and Associate Professor Ambarish Ghosh, uses a
focused laser beam to trap and manoeuvre a nano-sized silver disk, which in
turn can attract and ensnare nanoparticles when light is shone on it.

The ability to trap and
manipulate microscopic objects using light — a Nobel Prize-winning advancement
— has led to breakthroughs in many fields. Called “optical tweezers”,
they, however, are not efficient at capturing nano-sized particles.

Researchers overcame this challenge
with what are called “plasmonic tweezers”, which can trap much
smaller particles, such as viruses or quantum dots, at lower light intensities.
The plasmonic tweezers use metallic nanostructures such as gold or silver,
which generate strong electromagnetic field around themselves when light hits
them, and this field attracts and traps nanoparticles. But, unlike optical
tweezers, they are fixed at a spot and can only capture particles close to
them.

In their earlier work, researchers hadmanaged to transport
nano-scale cargo
using plasmonic tweezers integrated with magnetic
nano-robots. However, the tweezers could not be used for certain types of
colloids such as magnetic nanoparticles. In the new study, ​ published in Nature
Communications
, the team has developed nano-manipulation technique
that works on optical forces alone, and is therefore more easily applicable to
standard lab-on-chip technologies.

They used a nano-disk made of silver as a plasmonic tweezer and maneuvered
it using a focused laser beam that acted as an optical tweezer. This allowed
them to manipulate nanoparticles even in magnetic colloids and biological
buffer solutions.

The researchers said that
the new approach could be used to precisely capture, transport and release
particles such as nano-diamonds or quantum dots. As it uses low-intensity
light, the approach would also enable non-invasive manipulation of fragile
biological specimens
such as bacteria, viruses and proteins,
according to a press release from the institute.

“What we have achieved is the capability of manipulating very,
very small particles, with much lower light intensity. This is important for
things that can be damaged, such as living cells, or even non-living things
where high-intensity beams can heat up the material,” said Ambarish Ghosh.

(India Science Wire)

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