A patterned and
cylindrical structure made up of carbon nanotubes.
Courtesy of the
researchers
(December 21, 2015) Nanotube “forest” in a microfluidic
channel may help detect rare proteins and viruses.
Engineers at MIT have devised a new technique for trapping
hard-to-detect molecules, using forests of carbon nanotubes.
The team modified a simple microfluidic channel with an
array of vertically aligned carbon nanotubes — rolled lattices of carbon atoms
that resemble tiny tubes of chicken wire. The researchers had previously
devised a method for standing carbon nanotubes on their ends, like trees in a
forest. With this method, they created a three-dimensional array of permeable
carbon nanotubes within a microfluidic device, through which fluid can flow.
Now, in a study published this week in the Journal of
Microengineering and Nanotechnology, the researchers have given the nanotube
array the ability to trap certain particles. To do this, the team coated the
array, layer by layer, with polymers of alternating electric charge.
“You can think of each nanotube in the forest as being
concentrically coated with different layers of polymer,” says Brian Wardle,
professor of aeronautics and astronautics at MIT. “If you drew it in
cross-section, it would be like rings on a tree.”
A zoomed in view
of carbon nanotubes, showing individual tubes.
Depending on the number of layers deposited, the researchers
can create thicker or thinner nanotubes and thereby tailor the porosity of the
forest to capture larger or smaller particles of interest.
The nanotubes’ polymer coating may also be chemically
manipulated to bind specific bioparticles flowing through the forest. To test
this idea, the researchers applied an established technique to treat the
surface of the nanotubes with antibodies that bind to prostate specific antigen
(PSA), a common experimental target. The polymer-coated arrays captured 40
percent more antigens, compared with arrays lacking the polymer coating.
Wardle says the combination of carbon nanotubes and
multilayer coatings may help finely tune microfluidic devices to capture
extremely small and rare particles, such as certain viruses and proteins.