STUDENT SUMMER RESEARCH
ambient (31.3 degrees C) and pressure of 72.9 atm, and because it has both gaslike and liquidlike
properties, it is an excellent non-polar solvent for many organic compounds, including caffeine.
“Supercritical fluid is also used to decaffeinate coffee,” says Poindexter. The extraction pro-
cess is fairly simple she says and only requires that supercritical carbon dioxide be forced
through green coffee beans. The supercritical fluid penetrates the beans and dissolves nearly
all of the caffeine present.
Gas Transport
Scott Butters ’10, Seung Kyu (Sean) Kim ’10, Ashley Nelson ’11, Thomas Oh ’10 and
Vincent Shieh ’12 spent the summer making membranes with professor of engineering Nancy
Lape. Their main goal was to increase permeation and selectivity of the polymer membranes
by creating membranes tailored to optimally separate a specific set of gases. The gases have
different permeabilities (which is the product of solubility).
The polymer membranes are all solid but gases diffuse through the membrane because of
a partial pressure gradient. Gases absorb on the polymer, diffuse through it and come off the
membrane on the other side. The permeability of the membrane is highly dependent on the
amount of fractional free volume (FFV) that is present in the polymer and the membrane.
The membranes were made out of a variety of polymers like Polydimethylsiloxane (PDMS), a
rubbery polymer, and Poly(4-methyl-2-pentyne) (PMP), a glassy polymer. Membranes made
of rubbery polymers have high permeabilities but low selectivities, while membranes made of
glassy polymers have high selectivities but low permeabilities. If the permeability increases,
usually the selectivity decreases.
“There is usually a trade off between permeability and selectivity since selectivity is also
dependent on the FFV. It’s a little counter intuitive—the idea that putting impermeable par-
ticles in a permeable membrane will increase the permeability—but it’s true,” said Nelson.
Research on the polymers will continue thanks to a five-year grant from the National
Science Foundation.
From Space to China and Beyond
Six students were asked to design a system to measure time-of-flight of space particles using
a field programmable gate array (FPGA). They went a few steps further and designed four
systems comparing them across several different parameters. Their initiative earned them a
chance to present their paper, “Performance and Area Tradeoffs in Space-Qualified FPGA-
Based Time-of-Flight Systems,” in Beijing, China, over the summer.
Three members of the team, Austin Lee ’10, Kevin King ’10 and Whitney
Austin Lee ’10 at the Great Wall in China.
Hsiong ’09, made the trip to China. Hsiong, who presented the paper, said the group
came up with four different designs for measuring the time-of-flight of space particles
using an FPGA. The time-of-flight is the time it takes for a particle to travel from one
detector to another. Once you know how fast a particle is traveling, you can determine what that
particle is.
“(THE STUDENTS) WERE REALLY ON
“For example, if we sent a rocket into
space, at some point, say near Venus, we
TARGET THROUGHOUT THE PROJECT.”
can find out how much helium and ni-
trogen there is. And, if 50 years later we
send another rocket to the same area, we
can detect if something has changed and what that means about the universe around us,”
said Hsiong, who presented the paper in Beijing, and now works as an electrical engineer
at Raytheon.
The paper grew out of a Clinic project conducted last year. Southwest Research Institute asked
HMC students to come up with a way to do time-of-flight computations using an FPGA instead
of an application-specific, integrated circuit (ASIC). FPGAs cost on the order of hundreds or
18 Harvey Mudd College FALL/WINTER 2009
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36