The Berkeley Science Review: Articles

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Sticky Fingers
Thanks to recent work from UC Berkeley engineers, the makers of Scotch Tape may have to rethink their product line. Taking a cue from geckos—which can climb nearly any surface with their sticky but self-cleaning feet—Jongho Lee, a postdoc in Ronald Fearing's lab, has developed a material that can stick to both dry and wet surfaces, and even gets stickier with repeated cycles of adhesion and release. This sticky surface, made out of polypropylene, is covered with millions of microscopic "fingers" about 20 microns long (approximately one-fifth the thickness of a sheet of paper) and just 300 nanometers in diameter (about one-hundredth that of a human hair). If the material gets dirty, just stick it to a clean, dry surface. More of the contaminating particles' surface area is in contact with the glass than with the tiny hairs, so when the adhesive is pulled away, the particles stick preferentially to the glass, leaving a newly clean adhesive surface. Larger particles make more contact with the hairs than small particles do, so the larger the particle, the harder it is to shake off, but Fearing's material has shown great success getting rid of particles with a two micron diameter. This technology won't keep you from tracking mud into your house on a rainy day, but it may very well make its way into the next generation of exploration robots—geckos in space, anyone?
--Jesse Dill

Looking for Bosons
The Large Hadron Collider (LHC), powered up for the first time last fall by the European Organization for Nuclear Research (CERN), is the largest and most complex machine ever built. Its primary purpose is to smash beams of particles together, traveling in opposite directions inside a 17 mile underground tunnel at tremendous velocities. The much-hyped ATLAS experiment aims to support or disprove a quantum theory involving the Higgs boson, which would help explain how massless particles can have mass. As part of a huge international collaboration, scientists at the Lawrence Berkeley National Laboratory (LBL) designed and partially fabricated the distribution feed box (DFBX), connecting the LHC's cryogenic, electrical, and vacuum systems to the different colliders and to the CERN control center. The DFBX plays a role in all four major collider experiments: ALICE (A Large Ion Collider Experiment), ATLAS (A Toroidal LHC ApparatuS), LHCb (Large Hadron Collider beauty), and CMS (Compact Muon Solenoid). Growing anticipation was put on hold, however, as a faulty connection led to a helium leak that will delay a restart until September 2009.
--Laura Erickson

Hotwired
Fossil fuel combustion produces about 90% of the world's power, but in the process, 60 to 70% of the energy stored in the fuel is lost as heat. Devices to scavenge this heat and turn it into electricity, called thermoelectrics, have been around for decades—providing power for the deep space probes Voyager I and II, for example—but their efficiency is generally too low to compete with conventional electricity, making them impractical for most applications. Thermoelectrics produce electricity from a temperature difference, so the ideal material for such a device conducts electricity well but can also maintain a temperature gradient.

Unfortunately, good electrical conductors also tend to conduct heat well. To solve this problem, Professors Peidong Yang and Arun Majumdar turned to silicon nanowires that decouple electrical and thermal conductivity. The nanowires are so tiny (about 100 nanometers in diameter, or one-thousandth the diameter of a human hair) that they cannot sustain the vibrations that would result in heat transfer, and etching the nanowires to roughen their surface restricts the vibrations even further. While the heat conductivity is greatly restricted, the electrical conductivity remains relatively robust, leading to an efficient thermoelectric device. While these devices are not yet ready for large-scale use, they may bring us one step closer to the thermoelectric dream. As graduate student Michael Moore says, "You're basically getting something from nothing."
--Jasmine McCammon

Mars in your backyard
Most canyons result from gradual geological processes over millions of years, but short, massive deluges of water can also scoop out a chasm. For example, geomorphologist Michael Lamb and his colleagues from the UC Berkeley BioMARS project believe that a sudden megaflood carved the amphitheater-headed Box Canyon in southern Idaho. Amphiteater-headed canyons, so named because they end in round, steep walls, are usually found in soft, sandy conditions and are thought to result from groundwater emerging as springs to erode the canyon walls, but Box Canyon is carved into much harder basalt, which made Lamb and his coworkers give it a second look. The canyon currently has no surface water flow, but Lamb believes that the many depressions, or "plunge pools," at the canyon's base were formed by ancient waterfalls. Its head also has telltale scour marks likely left by surface water. And the team's calculations indicate that only vast amounts of very fast-flowing water could have moved the massive boulders downstream to their current resting places. They estimate that the canyon, up to 70 meters deep in some places, was formed by a flood lasting only 35 to 160 days. Of particular interest are the similarites between Box Canyon and amphitheater-headed canyons on Mars, also carved into basalt. If the Martian canyons evolved in the same way, through flooding rather than groundwater erosion, this could shed light on unanswered questions about water's role in the Red Planet's past.
--Sharmistha Majumdar

Look both ways
Not satisfied with your 20/20 vision? How about 20/8? Austin Roorda can give it to you, as long as you're looking into his machine. Roorda, chair of the UC Berkeley Vision Science Graduate Group, has developed the Adaptive Optics Scanning Laser Ophthalmoscope, or AOSLO, a machine that allows him to see your retina—and you to see images—with unprecedented clarity. Adaptive optics was originally developed by astronomers to eliminate distortions in their images by measuring and correcting for fluctuations in the atmosphere between the stars and their telescopes. For Roorda's application, he says, "adaptive optics is a way to remove the blur caused by imperfections in the eye's optics," including the lens, cornea, vitreous humor, and even the film of tears that covers the eye, all of which are constantly changing. AOSLO uses a laser to detect aberrations in the eye and then corrects the image—or adapts—in real time. The correction works both ways: Roorda sees clearer images of patients' retinas, and patients see extremely crisp images projected by the laser directly onto their retinas. Roorda's first goal is to screen patients for eye diseases by examining the retina on a cellular level. He also aims to test the limits of human vision. Theoretically the retina limits our visual acuity to roughly 20/8, and one subject, with the help of the AOSLO, has achieved this limit. Whether it's peering into the furthest skies or depths of eyes, adaptive optics provide great insight.
--Chat Hull

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