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Lead author Carlos J. Hernandez, a UCLA chemistry
graduate student, designed a customized font for the letters and
produced them.
“We have demonstrated the power of a new method, at
the microscale, to create objects of precisely designed shapes that
are highly uniform in size,” said Mason, a member of UCLA’s California
NanoSystems Institute. “They are too small to see with the unaided eye,
but with an optical microscope, you can see them clearly; the letters
stand out in high fidelity. Our approach also works into the nanoscale.”
Hernandez and Mason also have produced particles
with different geometric shapes, including triangles, crosses and
doughnuts, as well as three-dimensional “Janus particles,” which have
two differently shaped faces.
“We have made fluorescent lithographic particles,
we have made complex three-dimensional shapes and, as shown by UCLA
postdoctoral fellow Kun Zhao, we can assemble these particles, for
example, in a lock-and-key relationship,” said Mason, whose research
is at the intersection of chemistry, physics, engineering and biology.
“We can mass-produce complex parts having different controlled shapes
at a scale much smaller than scientists have been able to produce
previously. We have a high degree of control over the parts that we
make and are on the verge of making functional devices in solution. We
may later be able to configure the parts into more complex and useful
assemblies.
“How can we control and direct the assembly of tiny
components to make a machine that works?” Mason asked. “Can we cause
the components to fit together in a controlled way that may be useful
to us? Can we create useful complex structures out of fundamental
parts, in solution, where we can mass-produce a small-scale engine,
for example? We will pursue these research questions.”
Because each letter is smaller than many kinds of
cells, possible applications include marking individual cells with
particular letters. It may be possible, Mason said, to use a molecule
to attach a letter to a cell’s surface or perhaps even insert a letter
inside a cell and use the letter-marker to identify the cell. The
research also could lead to the creation of tiny pumps, motors or
containers that could have medical applications, as well as security
applications.
In addition to creating the letters, Mason’s
research group can pick up letters and reposition and reorient them in
a microscale version of the game Scrabble (see image).
“We have used ‘laser tweezers’ to pick up the
jumbled letters ‘U, C, L, A’ and move them together in order, like
skywriting in solution,” Mason said. UCLA chemistry graduate student
James Wilking moved the letters to spell “UCLA.”
Mason’s research is funded in part by the National
Science Foundation. He also receives research support from UCLA’s John
McTague Career Development Chair, which provides research funding for
five years.
“UCLA’s Office of Intellectual Property has applied
for patent protection on this platform technology and is beginning to
speak with potential corporate partners to bring new products to
market based on this technology to benefit the public good,” said Earl
Weinstein, who handles technology business development and licensing
for UCLA’s technology transfer office.
As a graduate student at Princeton in the early
1990s, Mason founded a field called “thermal microrheology,” the
techniques of which are now used by scientists worldwide.
Microrheology is a method for examining the viscosity and elasticity
of soft materials, including liquids, polymers and emulsions, on a
microscopic scale. Mason and Hernandez’s research in the Journal of
Physical Chemistry C provides novel probes for microrheology.
For centuries, scientists and engineers have
studied the deformation and flow, or rheology, of soft materials on a
large, laboratory scale. However, until Mason developed the field of
microrheology, which relies on the random Brownian motion of probe
particles, scientists had not done so on the microscopic level.
As with much cutting-edge science, Mason’s research
opens up the possibility for developments that sound like science
fiction. Are microscale devices that can actively identify cancer
cells and eliminate them a real possibility? Could Mason’s research
help achieve this goal? The answer, he said, will probably not come
anytime soon, but perhaps in his lifetime. Understanding microrheology
in synthetic materials is the first step to understanding what occurs
in active materials like the interior of cells and may help us
understand how cells function while alive and how they die. |
