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Pomona
Students, Professor Publish Laser Tweezers Research In
Professional Journal
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Late last year, Pomona College students Perry Schiro, Class
of 2004, and Christopher DuBois, Class of 2006, had their
research on “Large capture-range of a single-beam gradient
optical trap” published in Optics Express, a professional
scientific journal produced by the Optical Society of
America.
In layman’s terms, they used a single highly focused laser,
like a very tiny Star Trek tractor beam, and found that the
radius of the capture range was up to ten times the distance
scientists previously thought it was. Schiro noted, “It's
useful if you want to manipulate cells or other spherical
objects non-intrusively.” Applications in molecular biology
and other areas are possible. The paper was co-authored with
Alfred Kwok, a professor of physics at Pomona.
Schiro, now a senior, first started working in Kwok’s lab
the summer after his freshman year and built the original
laser tweezers setup with little supervision. The next
summer, Perry took the lead in the lab, continuing the work
and making additions to the laser tweezers setup in Kwok’s
absence. “I'm still picking up all the intricacies,” Kwok
admits.
The potential of laser tweezers was first observed in 1986
by A. Ashkin et al. They discovered that when a tightly
focused laser was aimed into a group of micron-sized (1
micron = 10-6 meters) glass or polystyrene beads suspended
in a solvent, a bead will be drawn to and then trapped at
the focal point of the laser. In order to understand why
this works it is simplest to think of a marble rolling
around in a bowl; the marble will eventually come to rest in
the center of the bowl because that is where it will have
the lowest potential energy. Similarly, the laser creates a
capture-range where the lowest potential energy is at the
focal point, so the beads are drawn there.
For over 15 years, it was thought that this capture-range
was only efficient at a distance of about one bead-radius.
However, during Schiro’s second summer, he and Kwok noticed
that beads were being drawn in from significantly greater
distances. In the summer of 2003, they decided to test this
property. DuBois, then a freshman, joined the team,
collecting data and brainstorming solutions to problems that
would arise. “There's a lot of problem solving that goes on
in the lab; it almost never work the way you want it to,”
DuBois said.
Together, Schiro, DuBois and Kwok collected research showing
that polystyrene beads roughly six to ten microns in
diameter could be captured from an initial distance of
approximately 100 microns from the trap-center. Their paper
was published in the 15 December 2003 release of Optics
Express. The full paper can be seen at www.opticsexpress.org
under the archives.
(more)
Both Schiro and DuBois conducted their summer research with
Kwok through Pomona College’s Summer Undergraduate Research
Program (SURP). Each student in SURP is given $375/week for
up to ten weeks of participation, and Pomona College pays
for the professors’ lab equipment, which in this case was
approximately $60,000 of tools, all state of the art. In the
school spirit of promoting undergraduate research, Professor
Kwok said, “I look for specific research projects that can
involve students.”
Schiro, a physics major with a chemistry minor, comes from
Marin County and attended The Branson School. He has played
lacrosse for six years and is now captain of Pomona
College’s state champion lacrosse team. His other sports
interests include volleyball and soccer. He has applied to
Stanford, Caltech, UCSB, and other renowned graduate schools
and is still waiting to hear back from most. After obtaining
his Ph.D., Perry plans to go into the scientific business
industry but has not ruled out becoming a professor. His
parents are Bob and Doreen Schiro, also residents of Marin
County.
DuBois attended Jesuit High School in Portland, Oregon, and
is in the process of deciding between a major in physics or
mathematics. This summer, he will help Professor Ami
Radunskaya develop computer programs to model tumor growth.
His future may include graduate school, but for now he isn’t
looking that far ahead. Formerly a cross-country runner,
Chris has recently decided to take up biking, putting much
of his summer research money into a new bike. He finished
second in his first race. Chris’s other interests include
camping, hiking, skateboarding, snowboarding, and the
ever-popular college game, Beirut. His parents, Lloyd and
Polly DuBois, are also residents of Portland.
Contact:
Perry Schiro
Phone: (909) 607-2392
Email: perry.schiro@pomona.edu
Christopher DuBois
Phone: (909) 607-5511
Email: christopher.dubois@pomona.edu
Alfred Kwok
Assistant Professor of Physics
Office Phone: (909) 621-8729
Email: alfred.kwok@pomona.edu |
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