Saturday, October 27, 2007
Dusty Galaxies Yield Up Hundreds Of Black Holes
Astronomers using specialized NASA telescopes have found hundreds of quasar/black holes hiding deep inside dusty galaxies billions of light-years away.
For decades, astronomers have long suspected that the universe held more quasars/black holes but were unable to discover where to look to find them until recently.
The newfound quasars are helping answer fundamental questions about how massive galaxies evolve. For example, astronomers have learned that most massive galaxies steadily build up their stars and black holes simultaneously until they get too big and their black holes suppress star formation.
The observations also suggest that collisions between galaxies might not play as large a role in galaxy evolution as previously believed, here on this Oblate Spheroid.
A growing black hole, called a quasar, can be seen at the center of a faraway galaxy in this artist's concept. Astronomers using NASA's Spitzer and Chandra space telescopes discovered swarms of similar quasars hiding in dusty galaxies in the distant universe. The Spitzer observations were made as part of the Great Observatories Origins Deep Survey program, which aims to image the faintest distant galaxies using a variety of wavelengths. -- Image Credit: NASA/JPL-Caltech
This from NASA (National Aeronautics and Space Administration) Mission News -
Missing Black Hole Report: Hundreds Found!
NASA -- Pasadena, Calif. -- 10.25.07
Astronomers have unmasked hundreds of black holes hiding deep inside dusty galaxies billions of light-years away.
The massive, growing black holes, discovered by NASA's Spitzer and Chandra space telescopes, represent a large fraction of a long-sought missing population. Their discovery implies there were hundreds of millions of additional black holes growing in our young universe, more than doubling the total amount known at that distance.
"Active, supermassive black holes were everywhere in the early universe," said Mark Dickinson of the National Optical Astronomy Observatory in Tucson, Ariz. "We had seen the tip of the iceberg before in our search for these objects. Now, we can see the iceberg itself." Dickinson is a co-author of two new papers appearing in the Nov. 10 issue of the Astrophysical Journal. Emanuele Daddi of the Commissariat a l'Energie Atomique in France led the research.
The findings are also the first direct evidence that most, if not all, massive galaxies in the distant universe spent their youths building monstrous black holes at their cores.
For decades, a large population of active black holes has been considered missing. These highly energetic structures belong to a class of black holes called quasars. A quasar consists of a doughnut-shaped cloud of gas and dust that surrounds and feeds a budding supermassive black hole. As the gas and dust are devoured by the black hole, they heat up and shoot out X-rays. Those X-rays can be detected as a general glow in space, but often the quasars themselves can't be seen directly because dust and gas blocks them from our view.
Daddi and his team initially set out to study 1,000 dusty, massive galaxies that are busy making stars and were thought to lack quasars. The galaxies are about the same mass as our own spiral Milky Way galaxy, but irregular in shape. At 9 to 11 billion light-years away, they existed at a time when the universe was in its adolescence, between 2.5 and 4.5 billion years old.
When the astronomers peered more closely at the galaxies with Spitzer's infrared eyes, they noticed that about 200 of the galaxies gave off an unusual amount of infrared light. X-ray data from Chandra, and a technique called "stacking," revealed the galaxies were, in fact, hiding plump quasars inside. The scientists now think that the quasars heat the dust in their surrounding doughnut clouds, releasing the excess infrared light.
"We found most of the population of hidden quasars in the early universe," said Daddi. Previously, only the rarest and most energetic of these hidden black holes had been seen at this early epoch.
"Theorists thought that mergers between galaxies were required to initiate this quasar activity, but we now see that quasars can be active in unharassed galaxies," said co-author David Alexander of Durham University, United Kingdom.
The new observations were made as part of the Great Observatories Origins Deep Survey, the most sensitive survey to date of the distant universe at multiple wavelengths.
Consistent results were recently obtained by Fabrizio Fiore of the Osservatorio Astronomico di Roma, Italy, and his team. Their results will appear in the Jan. 1, 2008, issue of Astrophysical Journal.
Wednesday, October 17, 2007
Crucible Of Marine Life Explored - New Species Found
A joint team of Filipino and American scientists that explored the Celebes Sea in southern Philippines early this month, announced the marine-life discoveries following their return from their voyage Tuesday.
This area of the Pacific Ocean, which is commonly referred to as the “Coral Triangle” (a region bordered by the Philippines, Malaysia and Indonesia), is suspected to be the crucible of marine life here on the Oblate Spheroid.
In this photo, a sample of zooplankton collected with a Tucker Trawl with a 10mm opening wherein one can find jellyfish, a lanternfish, a snipe eel, two orange shrimp, a pyrosome (which is bioluminescent) as shown at a briefing Tuesday Oct. 16, 2007 aboard the Philippine research vessel BRP Prisbitero off Manila Bay in Manila, Philippines. Image Credit: AP Photo/WHOI/ISSP, Larry Madin HO
Scientists have long recognized this area as having a high degree of biological diversity.
The deepest part of the Celebes Sea is 16,500 feet. The team was able to explore and catalog marine life to a depth of about 9,100 feet using a remotely operated camera.
This excerpted from AP via YAHOO! NEWS -
Scientists discover rare marine species
By OLIVER TEVES, Associated Press Writer (MANILA, Philippines) - Tue Oct 16, 7:36 PM ET
Scientists exploring a deep ocean basin in search of species isolated for millions of years found marine life believed to be previously undiscovered, including a tentacled orange worm and an unusual black jellyfish.
Project leader Dr. Larry Madin said Tuesday that U.S. and Philippine scientists collected about 100 different specimens in a search in the Celebes Sea south of the Philippines.
"This [The Coral Triangle] is probably the center where many of the species evolved and spread to other parts of the ocean, so it's going back to the source in many ways," Madin told a group of journalists, government officials, students and U.S. Ambassador Kristie Kenney and her staff.
In this photo, a jellyfish (Aequorea sp) collected by divers in the surface waters of the Celebes Sea in southern Philippines. A joint team of Filipino and American scientists that explored the Celebes Sea in southern Philippines early this month, announced the marine-life discoveries following their return from their voyage Tuesday. Image Credit: AP Photo/Ocean Geographic Magazine through WHOI/ISSP, Michael Aw, HO
The project involved the Woods Hole Oceanographic Institution and National Geographic Magazine in cooperation with the Philippine government, which also provided the exploration ship.
The expedition was made up of more than two dozen scientists and a group from National Geographic, including Emory Kristof, the underwater photographer who was part of the team that found the wreckage of the Titanic in 1985.
Madin said the specimens they collected included several possibly newly discovered species. One was a sea cucumber that is nearly transparent which could swim by bending its elongated body. Another was a black jellyfish found near the sea floor.
The most striking creature found was a spiny orange-colored worm that had 10 tentacles like a squid, Madin said. "We don't know what it is ... it might be something new," he said.
Madin said the Celebes Sea, being surrounded by islands and shallow reefs, is partially isolated now and may have been more isolated millions of years ago, leading scientists to believe that "there may be groups of organisms that have been contained and kept within" the basin since then.
"That makes it an interesting place to go and look to see what we might find," he said.
Monday, October 15, 2007
Spherical Solar Cell Production Breakthrough
Traditional solar cell production techniques require the use of more silicon and are inflexible as to the shape the cell arrays can be made into.
This breakthrough in the way solar cells are created utilizes gravity to form the crystallized silicon into energy converting spheres. The spherical shape allows the silicon cell to grab and convert light from any direction … even light that bounces off of our Oblate Spheroid.
The reason why a room does not become dark even if it does not receive direct sunlight is a variety of reflected and diffused light. However, conventional flat solar cells were unable to effectively harness this indirect light. In addition, the sun takes on a many different positions according to the season and time of day, so in order to obtain a stable supply of power, there was a need to change the orientation of the solar cell by constantly following the sun. Sphelar® captures light from all directions, which means it can catch reflected light and diffused light. In addition, there is no need for the superfluous operation of tracking the sun. The spherical light-receiving surfaces achieve unprecedented high generation efficiency. Caption & Image Credit: Kyosemi Corporation
This edited from Digital World (Tokyo) via SlashDot -
1mm diameter solar cell spheres formed in freefall by gravity
By J Mark Lytle - Digital World (Tokyo) October 12th, 2007
The traditional flat solar panel looks like becoming a thing of the past now that a Japanese company has developed a spherical equivalent that is both more efficient and far cheaper to make.
Conventional flat solar cells are produced by slicing crystalline silicon ingots, generating a large quantity of "Kerf loss" in the production process. In contrast, Sphelar is produced using a unique process whereby melted silicon is subjected to free fall, and spheres are formed naturally by the microgravity conditions, so there is hardly any waste of raw materials at all. This results of course in a dramatic reduction in costs, and helps ensure the efficient use of silicon, a finite resource. Sphelar is an environmentally-friendly product, not only in terms of performance but also during the production phase. Caption & Image Credit: Kyosemi Corporation
The Sphelar, which is the brainchild of Kyoto-based Kyosemi, is a perfectly round solar cell that can be made as small as 1mm in diameter. In serial or parallel, hundreds or thousands of the devices can be used to form a solar panel of any shape.
While it may not seem like a major difference, the practical effect of making a non-flat solar panel is that it doesn’t have to precisely face the sun to capture energy. In fact, Sphelar cells can generate electricity from both direct and indirect sunshine; effectively soaking up available light whatever direction it comes from.
Construction methods are also efficient - less silicon is needed to make a Sphelar than a conventional solar cell as the spheres are crystallized out of molten silicon by gravity during freefall from 14m. Standard cell manufacturing results in half as much silicon being wasted as is actually used.
Perhaps the most flexible aspect of the new cells is their ability to be molded into any shape needed and placed in any location. Possibilities include solar panels in awkward places or even windows that generate electricity through Sphelar cells embedded in the glass.
Wednesday, October 10, 2007
Serious Sustainability - From “Biosphere” to Luna Gaia
One of the largest problems of living outside of this Oblate Spheroid is the sustainability of human life with air, water, and an adequate food source.
Early efforts to create closed capsule-like living environments, like “Biosphere 2” in the Arizona desert, ended up looking more like an attempt at performance art than an effort focused on serious sustainability.
The best efforts at sustainability have only been able to be successful for a short time where as a team led by Australian scientists feel they have come up with a design of habitat that will be able to be 90% to 95% self-sufficient.
Luna Gaia is the latest of these efforts and it has come to light recently in a talk detailing the design at the Australian Space Science Conference held in Sydney last month.
This from Cosmos Online via SlashDot -
Self-sufficient space habitat designed
By Carolyn Barry, Cosmos Online - Tuesday, 9 October 2007
The development of such as system could save billions of dollars in shuttle trips to re-supply lunar or space colonies and brings closer the vision of a human habitat on Mars.
Some systems to recycle water and air have already been developed and rudimentary versions are presently used in the International Space Station (ISS). However, the proposed new lunar habitat "combines our existing knowledge" of physical, chemical and biological processes to provide an "overall picture of how a minibiosphere would work," said James Chartres aerospace engineer at the University of Adelaide in South Australia.
Biosphere 2, under the management of The University of Arizona, is one of the world's most unique facilities dedicated to the research and understanding of global scientific issues. In addition to its popular daily tours of Biosphere 2, The University of Arizona has established two additional scientific entities, B2 Earthscience and B2 Institute, dedicated to achieving a range of research, education, and outreach goals. Image Credit: University of Arizona
The project is in some ways similar to the failed Biosphere 2 experiment, built in Arizona, U.S., in the late 1980s. Over an area of 12,000 m2, Biosphere housed a closed ecological system, incorporating a mini 'ocean' with coral reefs, as well as a grassland, desert, mangrove, rainforest and agricultural areas. Eight people survived in the habitat for two years, but a lack of food and low levels of oxygen hampered the experiment. Chartres detailed plans for a smaller, space-bound concept, dubbed Luna Gaia.
Devised by an international team of 30 space scientists, Luna Gaia would be a 'closed-loop' environment, meaning that almost all material within the system is recycled with very little need for input from outside sources. The current design caters for a team of 12 astronauts under isolation for up to three years.
The Luna Gaia concept integrates technologies such as the Closed Equilibrated Biological Aquatic System (CEBAS), an enclosed aquarium designed by the German Aerospace Centre and the Micro-Ecological Life Support System Alternative (MELIiSSA) developed by the European Space Agency. MELIiSSA uses microbes to purify water, recycle carbon dioxide and derive edible material from waste products.
Algae – which generates oxygen from carbon dioxide via photosynthesis, and doesn't require pollinating – is the key to the proposed design.
The food required for astronauts would come from a mixture of tending small crops and from pre-packed supplies. Such crops would include peanuts, lettuce, tomatoes, carrots and wheat. In addition, certain types of algae, such as Spirulina or Chlorella would provide other vitamins, minerals and trace elements.
The diet would be largely vegetarian, said Chartres, but protein could potentially come from small-scale farming of fast-growing fish such tilapia.
A lunar base is unlikely to ever be 100 per cent self-sufficient, said Chartres, because no atmosphere is completely safe from leaks and it could not provide humans with all the nutrients that they need to survive.
Moreover, astronauts need the occasional break to the routine of standard food, so the odd "luxury item such as fruit salad, spices or chocolate," would ward off any doldrums, he said.
Pathogens introduced to the system by plants, as well as difficulties of pollination for crops still pose significant hurdles to the design. In addition, as much as 20 m2 of plants would be required to feed a single astronaut.
The proposed system, is unlikely to be up and running any time soon. Chartres estimates it will be another 20 to 30 years before the funding for the set-up and the practicality of providing the space for plant growth in a spacecraft is realised.
"This is an issue that is not only important for future long duration human space missions, but for humans on Earth as well," said [Mark Kliss, a bioengineer with the NASA Space Biosciences Division in Moffett Field, California].
And this, one of the comments posted below the article in Cosmos Online proposed the following:
Tilapia? How about a can of Worms?
Ok, leave your cultural biases at the door if you mainly live in Europe or the USA, are they at the door? Ok then...
The article mentions that the astronauts could grow tilapia as a protein source?!?
Oh wait, they could also grow some cows, I hear those are really efficient...Microlivestock (INSECTS) is a much better choice as a protein source for astronauts, as well as vitamins, minerals and fiber (chitin).
Because people don't eat insects as food in SOME parts of the world, doesn't mean they are not a healthy, delicious, and in this case efficient part of the human diet. Some insects have much better feed efficiencies than larger animals, and some (not all) can be grown in much closer proximity than larger animals. AND as a bonus, if we humans seize to exist on earth, and then supplies stop coming to the moon, them cockroaches will also outlast us in the moon and mars as well...
This comment is meant to be taken seriously, and before someone replies ignorantly or emotionally to it research about the subject...if your current society doesn't eat insects, it's neither good or bad, but it is your context, if you are grossed out try to view it from outside your current context.
Submitted by InsectMan on 10 October 2007 - 8:19am.
Finally, this excerpted and updated comment about the article from Luna Gaia project leader, James Chartres aerospace engineer at the University of Adelaide in South Australia -
Re: Self-sufficient space habitat designed
The actual study was done within a team of 32 professionals from 12 different countries and was not Australian led as we worked as a cohesive a team. The life support system design team consisted of 9 people from 6 different countries including Australia, Canada, China, Japan, Spain and the United Kingdom.
One of the aims of the research was to develop a life support system that would reduce the amount of required resupply. As mentioned in the article things like leakage, luxury items and spare parts prohibit the system from being completely self sufficient or closed loop. The research was intended to provide recommendations for future avenues of research and identify where current gaps are.
The reason for the large lead-time is that such a biological system on such a massive scale would take a long time to research and understand. Additionally, the construction and development of such a large system would take a long period of time due to the heavy lift capabilities required to get that much mass to the moon. Understanding such a complex system including the mass balance and where storage buffers would be required would need significant research and there are many issues to overcome. Studies have shown that the use of bio-regenerative methods only become feasible if mission durations exceed 2.5 to 3 years depending on the size of the crew. The 20 to 30 years is an estimate and like most research could change dramatically given the required resources and personnel.
We also actually looked at the possibility of including insects as a food source. There have been some published studies in Japan about the use of insect and as a source of protein they are another possible option that was considered and further research was recommended.
I recently spent 3 months in China interacting with students and also CASC the Chinese Aerospace Science and Technology Corporation. I would argue from my experience in China that the Chinese do not view space as a plaything and there is a tremendous amount of national pride for their space program. This is demonstrated in such things as astronaut images on bottle of water and the large amount of news coverage it receives on the CCTV stations.
Submitted by James Chartres on 10 October 2007 - 12:56pm.
Friday, October 5, 2007
Hook-Beaked Lizard Fossil Discovery In Utah
Gryposaurus monumentensis, a new and very large duck-billed dinosaur species was recently uncovered in Utah at the infamous Grand Staircase-Escalante national Monument. What makes this discovery unique is that not only did this creature have a set of intimidating teeth … it was very large.
The age of Gryposaurus is set to be back about 75 million years and is suspected to be the largest dinosaur found in this fossil strata formation.
While the teeth and the size of this discovery seem monstrous and threatening, not to worry, “Grypo” is a plant eater.
Utah Museum of Natural History researchers at the University of Utah prepared the skull of a new species of duck-billed dinosaur -- Gryposaurus monumentensis -- which was discovered in Grand Staircase-Escalante National Monument. Image Credit: Utah Museum of Natural History
This excerpted from a Newswise press release -
A Toothy New Duck-Billed Dinosaur from Southern Utah
Newswise - University of Utah - Released: Thu 27-Sep-2007, 22:00 ET - Embargo expired: Wed 03-Oct-2007
The newest dinosaur species to emerge from Grand Staircase-Escalante National Monument had some serious bite, according to researchers from the Utah Museum of Natural History at the University of Utah.
“It was one of the most robust duck-billed dinosaurs ever,” said museum paleontologist Terry Gates, who is also with the U.’s Department of Geology and Geophysics. “It was a monster.”
Researchers from the Utah museum, the national monument and California’s Raymond M. Alf Museum of Paleontology unearthed fossils of this ancient plant-eater from the rocks of the Kaiparowits Formation. Researchers announced the name of the creature – Gryposaurus monumentensis. (Gryposaurusmeans “hook-beaked lizard” and monumentensis honors the monument where the fossils were found.)
The first description of the duck-billed dinosaur – which dates to the Late Cretaceous Period 75 million years ago – appears in the Oct. 3 issue of the Zoological Journal of the Linnean Society.
“Gryposaurus monumentensis is probably the largest dinosaur in the 75-million-year-old Kaiparowits fossil ecosystem,” said Alan Titus, paleontologist for the national monument.
Gates, lead author on the study, explained that this creature could have eaten just about any vegetation it stumbled across. “With its robust jaws, no plant stood a chance against G. monumentensis,” he said.
Finding the skull
In 2002, a team from the Alf Museum, in Claremont, Calif., located at the Webb School, discovered the site that contained the skull used to describe the new creature.
The California team was working a stretch of Grand Staircase that Utah researchers had not examined. Duncan Everhart, a Pennsylvania furniture maker, is credited with finding the skull.
Don Lofgren, curator of the Alf Museum, said the team received permission from the monument to dig deeper in 2003.
“We determined it was a skull sitting upside down with the jaw on top,” he said.
Once Gates went out to take a look in 2004, he quickly realized the California team had a potentially-important find. The Alf Museum gave the Utah researchers permission to prepare and study the skull.
Titus noted the discovery of this new species was a team effort involving the Alf Museum, the Utah Museum of Natural History and the national monument.
“The cooperative effort put into its collection and research has truly been a model for scientific investigation on public lands,” he said.
It wasn’t until Utah researchers began working on the skull in 2005 that the full significance of the find began to emerge, Gates said.
The well-preserved skull was initially missing key pieces from the nose region. Fortunately, the California museum had collected a box full of eroded bones, including bits of the nose bone, which was critical for identifying the creature.
“I knew immediately that we had some species of Gryposaurus,” Gates said.
A toothy beast
The creature’s large number of teeth embedded in the thick skull is among the features that made G. monumentensis, as well as other closely related duck-billed dinosaurs, such a successful herbivore.
At any given time, the dinosaur had over 300 teeth available to slice up plant material. Inside the jaw bone, there were numerous replacement teeth waiting, meaning that at any moment, this Gryposaur may have carried more than 800 teeth.
While the diet is unknown, given the considerable size of the creature, the massive teeth and jaws are thought to have been used to slice up large amounts of tough, fibrous plant material.
The teeth may hold important clues the dinosaur’s eating habits. The Utah museum plans to study the composition of the dinosaur teeth, which when compared to other plant-eating dinosaurs from the Kaiparowits Formation, will help researchers decipher differences in diet.
Researchers believe the head of this particular Gryposaur likely rolled into a bend of a river, where it was partly buried. The right half of the head remained exposed to the river current, dislodging several bones before this side was buried as well.
In other parts of the monument, Utah researchers have excavated bones believed to be from the same species. Gates estimates G. monumentensis may have grown up to 30 feet long as an adult.
In what Sampson terms “West America,” G. monumentensis and its fellow dinosaurs lived in a narrow strip of land sandwiched between the seaway to the east and rising mountains to the west. Due in large part to the presence of the seaway, the climate was moist and humid.
Thanks to more than 100 years of fossil collection, scientists know more about the Cretaceous dinosaurs from North American than they do from any other time or continent on Earth, Sampson noted.
While G. monumentensis gulped down its greens and tried to avoid predatory tyrannosaurs down in Utah, closely related but different species of duck-billed dinosaurs were doing the same thing farther north, in places like Montana and Alberta, Canada.
The new Utah species is proving crucial for determining patterns of duck-billed dinosaur evolution and ecology during the Late Cretaceous of North America, Gates said. He added that “this calls for a re-evaluation of previous ideas about the evolution of duck-billed dinosaurs across the world”.
Bones from G. monumentensis are on display at Big Water Visitor Center in Grand Staircase-Escalante National Monument, and for a short time at the Utah Museum of Natural History before returning to the Alf Museum.
Tuesday, October 2, 2007
Bacteria Breakthrough For Microdot Printed Circuits
An E. Coli infection to the human body is not a good thing. The infection may create symptoms that include severe abdominal cramping, bloody diarrhea, and sometimes nausea with vomiting.
Bacteria, however, has enzyme properties that allow one to improve the preciseness of the surface pattern of a printed circuit one-hundred fold of traditional inking methods.
This discovery will have a tremendous effect on the depth of computer processes that can be placed on a single chip, in that, this inkless technique could be used to build complex nanoscale devices with unprecedented precision to create microdevices such as labs-on-a-chip.
This excerpted from Wikipedia –
1) After the discovery of microtechnology (~1958) for realizing integrated semiconductor structures for microelectronic chips, these lithography-based technologies were soon applied in pressure sensor manufacturing (1966) as well.
Due to further development of these usually CMOS-compatibility limited processes, a tool box became available to create micrometre or sub-micrometre sized mechanical structures in silicon wafers as well: the Micro Electro Mechanical Systems (MEMS) era (also indicated with Micro System Technology - MST) had started.
2) Lab-on-a-chip (LOC) is a term for devices that integrate (multiple) laboratory functions on a single chip of only millimeters to a few square centimeters in size and that are capable of handling extremely small fluid volumes down to less than pico liters. Lab-on-a-chip devices are a subset of MEMS devices and often indicated by "Micro Total Analysis Systems" (µTAS) as well.
Microfluidics is a broader term that describes also mechanical flow control devices like pumps and valves or sensors like flowmeters and viscometers. However, strictly regarded "Lab-on-a-Chip" indicates generally the scaling of single or multiple lab processes down to chip-format, whereas "µTAS" is dedicated to the integration of the total sequence of lab processes to perform chemical analysis.
Over time, this can have an effect on the general miniaturization of electronic devices. Hand held devices just may become finger held devices.
This excerpted EurekAlert! from Duke University –
Using catalysts to stamp nanopatterns without ink
Contact: Monte Basgall, Duke University - Public release date: 26-Sep-2007
Using enzymes from E. coli bacteria, Duke University chemists and engineers have introduced a hundred-fold improvement in the precision of features imprinted to create microdevices such as labs-on-a-chip.
Their inkless microcontact printing technique can imprint details measuring close to 1 nanometer, or billionths of a meter, the Duke team reported in the Sept. 24, 2007 issue of the Journal of Organic Chemistry.
"This has a lot of potential, because we don't have the resolution issue," said Robert Clark, a professor of mechanical engineering and materials science and dean at Duke’s Pratt School of Engineering. “The really important part is that with a biological catalyst there’s no ink involved,” added Duke chemistry professor Eric Toone.
Clark, Toone and three graduate students authored the report on their study, which was funded by the National Science Foundation (NSF).
In traditional microcontact printing -- also called soft lithography or microstamping -- an elastic stamp’s end is cast from a mold created via photolithograpy – a technique used to generate microscopic patterns with light. Those patterns are then transferred to a surface by employing various biomolecules as inks, rather like a rubber stamp.
A shortcoming of traditional microcontact printing is that pattern transfer relies on the diffusion of ink from the stamp to the surface. This same diffusion spreads out beyond the limits of the pattern as the stamp touches the surface, degrading resolution and blurring the feature edges, Clark and Toone said.
Because of this mini-blurring, the practical limit to defect-free patterning is “in excess of 100 nanometers,” said the report, whose first author, Phillip Snyder, is a former Toone graduate student now working as a postdoctoral researcher in Whitesides’ group.
A 100 nanometer limit of resolution is about 1,000 times tinier than a human hair’s width. While that seems very precise, the Duke team now reports it can boost accuracy limits to less than 2 nanometers by entirely eliminating inking.
Clark and graduate student Matthew Johannes crafted a microstamp out of a gel-like material called polyacrylamide, which compresses more uniformly than the silicone material known as PDMS which is normally used in microstamping.
In lieu of ink, Snyder, Toone and graduate student Briana Vogen suspended a biological catalyst on the stamp with a molecular “tether” of amino acids. For this proof-of-principle demonstration, Toone’s team chose as a catalyst the biological enzyme exonuclease I, derived from the bacterium E. coli.
In one set of experiments, the polyacrylamide stamp pattern bearing the tethered enzymes was then pressed on a surface of gold that had been covered with a uniform coating of single-stranded DNA molecules. The DNA molecules had also been linked to fluorescent dye molecules to make the coating visible under a microscope.
Wherever the enzyme met the DNA, the end of the DNA chain and its attached dye were broken off and removed. That created a dye-less pattern of dots on the DNA coating, each dot measuring about 10 millionths of a meter diameter each.
The microdots are very precise because the catalyst that created them could not shift its position more than the length of its chemical tether -- less than 1 nanometer, the Duke team reported. "Whether the stamp was left on for a short period of time, or for days, the pattern did not change,” Clark said.
The inkless microstamp could also re-use the same suspended catalyst molecule repeatedly. “Enzymes can deteriorate with extended use,” Clark acknowledged. “But because of our tether attachment chemistry, we can easily wash the old enzyme off, put on a new one and keep going,” Clark said.
In follow-up research, Clark and Toone are now evaluating more durable microstamping materials attached to longer lasting catalysts that are non-enzymatic.
“Soft lithography has really revolutionized the field of surface science over the last 30 years,” said Toone. “And I honestly believe that using catalysts instead of diffusive processes is going to become the way that soft lithography is done in the future.”