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3-D 'pop-up' silicon structures: Transforming planar materials into 3-D microarchitectures
Date:
January 8, 2015 Source:
University of Illinois College of Engineering
Researchers at the University of Illinois at Urbana-Champaign have developed a unique process for geometrically transforming two dimensional (2D) micro/nanostructures into extended 3D layouts by exploiting mechanics principles similar to those found in children's 'pop-up' books.
Complex, 3D micro/nanostructures are ubiquitous in biology, where they provide essential functions in even the most basic forms of life. Similar design strategies have great potential for use in a wide variety of human-made systems, from biomedical devices to microelectromechanical components, photonics and optoelectronics, metamaterials, electronics, energy storage, and more.
Researchers noted that existing methods for forming 3D structures are either highly constrained in the classes of materials that can be used, or in the types of geometries that can be achieved.
«Conventional 3D printing technologies are fantastic, but none offers the ability to build microstructures that embed high performance semiconductors, such as silicon», explained John Rogers, a Swanlund Chair and professor of materials science and engineering at Illinois. «We have presented a remarkably simple route to 3D that starts with planar precursor structures formed in nearly any type of material, including the most advanced ones used in photonics and electronics. A stretched, soft substrate imparts forces at precisely defined locations across such a structure to initiate controlled buckling processes that induce rapid, large-area extension into the third dimension. The result transforms these planar materials into well-defined, 3D frameworks with broad geometric diversity».
Potential applications range from battery anodes, to solar cells, to 3D electronic circuits and biomedical devices.
«The 3D transformation process involves a balance between the forces of adhesion to the substrate and the strain energies of the bent, twisted elements that make up the planar precursors», explained Sheng Xu, a postdoctoral fellow and co-author of the research paper. «Basically, we print 2D structures onto a pre-strained elastomer substrate with selected bonding points. Releasing the substrate to its original shape induces buckling processes that lift the weakly bonded regions of the 2D structure out of contact with the surface. The resulting spatially dependent deformations occur in an ordered sequence to complete the 3D assembly».
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These motions follow precisely the predictions of 3D computational models of the mechanics. These models, in turn, serve as rapid, inverse design tools for realizing a wide range of desired shapes.
Compatibility with the most advanced materials (e.g. monocrystalline inorganics), fabrication methods (e.g. photolithography) and processing techniques (e.g. etching, deposition) from the semiconductor and photonics industries suggest many possibilities for achieving sophisticated classes of 3D electronic, optoelectronic, and electromagnetic devices.
«With this scheme, diverse feature sizes and wide-ranging geometries can be realized in many different classes of materials», stated postdoctoral fellow and co-author Zheng Yan. «Our initial demonstrations include experimental and theoretical studies of more than forty representative geometries, from single and multiple helices, toroids and conical spirals, to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences and frameworks, each with single and/or multiple level configurations, constructed in various materials, including semiconductors, conductors and dielectrics».
«This work establishes the concepts and a framework of understanding. We're now exploiting these ideas in the construction of high performance electronic scaffolds for actively guiding and monitoring growth of tissue cultures, and networks for 3D electronic systems that can bend and shape themselves to the organs of the human body. We're very enthusiastic about the possibilities». Rogers added.
Rogers is the director of the Frederick Seitz Materials Research Laboratory and an affiliate of the Beckman Institute for Advanced Science and Technology at Illinois. He also holds affiliate appointments in the departments of bioengineering, chemistry, electrical and computer engineering, and mechanical science and engineering. With his research teams, Rogers has pioneered flexible, stretchable electronics, creating pliable products such as cameras with curved retinas, medical monitors in the form of temporary tattoos, a soft sock that can wrap an arrhythmic heart in electronic sensors, and LED strips thin enough to be implanted directly into the brain to illuminate neural pathways. His work in photovoltaics serves as the basis for commercial modules that hold the current world record in conversion efficiency.
This research was supported by the U.S. Department of Energy Office of Science
C o m p r e h e n s i o n
1.Read the article; as your read, note the topic dealt with in each paragraph, underline the topic sentence, key words, and important facts as your go along.
2.Analyze how the facts are connected, how the topic of a paragraph is connected with that of a preceding paragraph.
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3.Make a list of all points you are going to mention in your précis .Write them down using the necessary key terms. These notes must contain all the essential facts.
4.Write a précis of the article.
5.Sum up the main points presented in the article. Write the plan of the article in the form of statements.
6.Develop your plan into summary.
7.Make your summary coherent by a sparing use of connectors.
8.Look through your summary. Find the least important sentences and delete them out the remaining ones to produce a well-written, clear and concise summary.
9.Compare your summary with the one given below. Which one is better and why?
Researchers have invented simple routes to complex classes of 3-D micro/nanostructures in high performance materials, with relevance to electronics, photovoltaics, batteries, biomedical devices, and other microsystems technologies.
3D microstructures of device-grade silicon formed using concepts similar to those in children's 'pop-up' books. The images correspond to colorized scanning electron micrographs. The silicon has a thickness of 2 microns.
TEXT 14
Nanowire clothing could keep people warm, without heating everything else
Date:
January 7, 2015
Source: American Chemical Society
To stay warm when temperatures drop outside, we heat our indoor spaces -- even when no one is in them. But scientists have now developed a novel nanowire coating for clothes that can both generate heat and trap the heat from our bodies better than regular clothes. They report on their technology, which could help us reduce our reliance on conventional energy sources, in the ACS journal Nano Letters.
Yi Cui and colleagues note that nearly half of global energy consumption goes toward heating buildings and homes. But this comfort comes with a considerable environmental cost -- it's responsible for up to a third of the world's total greenhouse gas emissions. Scientists and policymakers have tried to reduce the impact of indoor heating by improving insulation and construction materials to keep fuel-generated warmth inside. Cui's team wanted to take a different approach and focus on people rather than spaces.
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The researchers developed lightweight, breathable mesh materials that are flexible enough to coat normal clothes. When compared to regular clothing material, the special nanowire cloth trapped body heat far more effectively. Because the coatings are made out of conductive materials, they can also be actively warmed with an electricity source to further crank up the heat. The researchers calculated that their thermal textiles could save about 1,000 kilowatt hours per person every year -- that's about how much electricity an average U.S. home consumes in one month.
C o m p r e h e n s i o n
1.Read the article; as your read, note the topic dealt with in each paragraph, underline the topic sentence, key words, and important facts as your go along.
2.Analyze how the facts are connected, how the topic of a paragraph is connected with that of a preceding paragraph.
3.Make a list of all points you are going to mention in your précis .Write them down using the necessary key terms. These notes must contain all the essential facts.
4.Write a précis of the article.
5.Sum up the main points presented in the article. Write the plan of the article in the form of statements.
6.Develop your plan into summary.
7.Make your summary coherent by a sparing use of connectors.
8.Look through your summary. Find the least important sentences and delete them out the remaining ones to produce a well-written, clear and concise summary.
9.Compare your summary with the one given below. Which one is better and why?
To stay warm when temperatures drop outside, we heat our indoor spaces -- even when no one is in them. But scientists have now developed a novel nanowire coating for clothes that can both generate heat and trap the heat from our bodies better than regular clothes. They now report on their technology, which could help us reduce our reliance on conventional energy sources.
Heat-based images show a conventional cloth glove (top) lets warmth escape while a nanowire glove traps it.
TEXT 15
New highly effective eco-friendly flame retardant
Date:
January 5, 2015 Source:
Stony Brook University
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Fire consumes wood ferociously, in a deadly blaze -- but the substances used to treat wood to resist burning can also be noxious and toxic. A Stony Brook University Materials Science Professor guided an undergraduate and two Long Island high school students as they developed a patent-pending, environmentally sustainable way to render the wood used in construction flame retardant -- and 5x stronger -- using natural materials.
«Our Office of Technology Transfer and Industry Relations has already gotten interest from several companies regarding possible license», says Miriam Rafailovich, who oversaw the research. Rafailovich is Distinguished Professor in the Department of Materials Science and Co-Director of the Program in Chemical and Molecular Engineering at Stony Brook University.
The work took place at the Garcia Center for Polymers at Engineered Interfaces at Stony Brook as part of the Garcia Research Scholar Program. The pre-college program offers the opportunity for high school students and teachers to perform research at the forefront of polymer science and technology alongside Garcia Center faculty and staff.
«The students were the primary drivers in this work; I guided them in addressing the pertinent questions», Rafailovich says. The research was initiated by Tehila Stone, a former student in the Garcia program. Stone worked as an undergraduate mentor at Stony Brook this past summer with the high school students, Daniel Kim and Noah Davis.
Davis, a senior at Earl L. Vandermuelen High School on Long Island, says he has always been interested in math and the sciences. «This led me to look for research programs over the summer. I learned about the Garcia Program, and the focus on polymer-based engineering immediately drew my interest». Kim, a senior at Smithtown High School West -- also on Long Island -- says «the Garcia Program was the optimal choice for access to a quality lab and great mentorship».
The team started off with a simple 2x4 from Lowe's; the flame retardant is a phosphor-based material safe for the environment. The researchers engineered a compound that impregnates wood's natural structure, forming a wood-plastic composite that exceeds UL 94 V-O criteria for safety of flammability. «The breakthrough was in the formulation of a compound that extinguishes a flame without decomposing into toxic byproducts», Rafailovich says.
That's ideal for the construction industry. Says Kim, «What interested me the most was that it could be used to safeguard homes and buildings. The idea that the world can really benefit from flame retardant wood was my greatest motivation for this project».
The interdisciplinary effort involved Dr. Marcia Simon, Professor and Director for Graduate Studies in the Department of Oral Biology and Pathology at the Stony Brook University School of Dental Medicine. Simon is also
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Director of the Living Skin Bank, and helped design the toxicology testing and evaluate EPA reports.
«The students chose to use resorcinol bis(diphenyl phosphate) (RDP), which the EPA has declared a preferred substitute for halogenated flame retardants», Simon says. «Preliminary data in our laboratory confirms that when RDP is reacted with cellulose, or clays, such as was done by the students, it is safe and non-cytoxic. Although the finished product is safe, in vitro tests suggest that the unreacted RDP liquid, used in industrial plants, can be cytotoxic and should be handled with care».
Rafailovich is pleased the young learners had this opportunity. «I believe that a great deal of innovation is possible if we encourage students to explore their ideas», she says. «Students are more in-tune than older adults with the latest science developments in the consumer arena, but don't have the tools and knowledge to act on these ideas. We hope that by helping them do that, they will learn the power of science and be inspired to remain in the field».
Davis certainly feels that way. «Dan and I worked with different chemicals and beakers to measure out volumes; we used heating ovens to create reactions between the wood and chemicals; after the wood samples were created, we tested their properties with the UL-94 flame test and an Izod impact test. While I already had a large interest in science before the program, the experience only furthered that interest. I currently want to study biomedical engineering, and see this as a direct result of my experiences within the program».
Says Rafailovich, «Stony Brook is a unique place where all this is possible. New science is problem-focused, and requires interdisciplinary collaborations across all areas of the campus. With its medical, dental, and engineering facilities, and proximity to Brookhaven National Laboratory and outstanding industrial parks, Stony Brook is ideal for this type of research».
It's also a good place for translating research into applications. «Our Office of Technology Transfer and Industry Relations is exceptional», Rafailovich says. «It requires a special staff to keep up with the diversity of science and industry, and over the years Stony Brook has established this network. A technology transfer staff that teaches and involves student is even rarer, making the Stony Brook years very memorable for any student who is fortunate to experience this».
C o m p r e h e n s i o n
1.Read the article; as your read, note the topic dealt with in each paragraph, underline the topic sentence, key words, and important facts as your go along.
2.Analyze how the facts are connected, how the topic of a paragraph is connected with that of a preceding paragraph.
116
3.Make a list of all points you are going to mention in your précis .Write them down using the necessary key terms. These notes must contain all the essential facts.
4.Write a précis of the article.
5.Sum up the main points presented in the article. Write the plan of the article in the form of statements.
6.Develop your plan into summary.
7.Make your summary coherent by a sparing use of connectors.
8.Look through your summary. Find the least important sentences and delete them out the remaining ones to produce a well-written, clear and concise summary.
9.Compare your summary with the one given below. Which one is better and why?
Fire consumes wood ferociously, in a deadly blaze—but the substances used to treat wood to resist burning can also be noxious and toxic. A professor guided an undergraduate and two high school students as they developed a patentpending, environmentally sustainable way to render the wood used in construction flame retardant—and 5x stronger—using natural materials.
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3.ДОПОЛНИТЕЛЬНЫЕ ТЕКСТЫ ДЛЯ ЧТЕНИЯ И ПЕРЕВОДА
Text 1
Civil Engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings. Civil engineering is the oldest engineering discipline after military engineering, and it was defined to distinguish non-military engineering from military engineering. It is traditionally broken into several sub-disciplines including environmental engineering, geotechnical engineering, structural engineering, transportation engineering, municipal or urban engineering, water resources engineering, materials engineering, coastal engineering, surveying, and construction engineering. Civil engineering takes place on all levels: in the public sector from municipal through to national governments, and in the private sector from individual homeowners through to international companies.
1.1. History of the civil engineering profession
Engineering has been an aspect of life since the beginnings of human existence. The earliest practice of civil engineering may have commenced between 4000 and 2000 BC in Ancient Egypt and Mesopotamia (Ancient Iraq) when humans started to abandon a nomadic existence, creating a need for the construction of shelter. During this time, transportation became increasingly important leading to the development of the wheel and sailing.
Until modern times there was no clear distinction between civil engineering and architecture, and the term engineer and architect were mainly geographical variations referring to the same person, often used interchangeably. The construction of Pyramids in Egypt (circa 2700–2500 BC) might be considered the first instances of large structure constructions. Other ancient historic civil engineering constructions include the Qanat water management system ( older than 3000 years and longer than 71 km,) the Parthenon by Iktinos in Ancient Greece (447–438 BC), the Appian Way by Roman engineers ( 312 BC), the Great Wall of China (220 BC) and the stupas constructed in ancient Sri Lanka like the Jetavanaramaya and the extensive irrigation works in Anuradhapura. The Romans developed civil structures throughout their empire, including especially aqueducts, insular, harbors, bridges, dams and roads.
In the 18th century, the term civil engineering was coined to incorporate all things civilian as opposed to military engineering. The first self-proclaimed civil engineer was John Smeaton who constructed the Eddy stone lighthouse. In 1771 Smeaton and some of his colleagues formed the Smeatonian Society of Civil Engineers, a group of leaders of the profession who met informally over dinner. Though there was evidence of some technical meetings, it was little more than a social society.
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In 1818 the Institution of Civil Engineers was founded in London, and in 1820 the eminent engineer Thomas Telford became its first president. The institution received a Royal Charter in 1828, formally recognizing civil engineering as a profession. Its charter defined civil engineering as the art of directing the great sources of power in nature for the use and convenience of man, as the means of production and of traffic in states, both for external and internal trade, as applied in the construction of roads, bridges, aqueducts, canals, river navigation and docks for internal intercourse and exchange, and in the construction of ports, harbors, moles, breakwaters and lighthouses, and in the art of navigation by artificial power for the purposes of commerce, and in the construction and application of machinery, and in the drainage of cities and towns.
The first private college to teach Civil Engineering in the United States was Norwich University founded in 1819 by Captain Alden Partridge. The first degree in Civil Engineering in the United States was awarded by Rensselaer Polytechnic Institute in 1835. The first such degree to be awarded to a woman was granted by Cornell University to Nora Stanton Blatch in 1905.
1.2. History of civil engineering
Civil engineering is the application of physical and scientific principles, and its history is intricately linked to advances in understanding of physics and mathematics throughout history. Because civil engineering is a wide ranging profession, including several separate specialized sub-disciplines, its history is linked to knowledge of structures, materials science, geography, geology, soils, hydrology, environment, mechanics and other fields.
Throughout ancient and medieval history most architectural design and construction was carried out by artisans, such as stonemasons and carpenters, rising to the role of master builder. Knowledge was retained in guilds and seldom supplanted by advances. Structures, roads and infrastructure that existed were repetitive, and increases in scale were incremental.
One of the earliest examples of a scientific approach to physical and mathematical problems applicable to civil engineering is the work of Archimedes in the 3rd century BC, including Archimedes Principle, which underpins our understanding of buoyancy, and practical solutions such as Archimedes' screw. Brahmagupta, an Indian mathematician, used arithmetic in the 7th century AD, based on Hindu-Arabic numerals, for excavation (volume) computations.
1.3. The civil engineer
Civil engineers typically possess an academic degree with a major in civil engineering. The length of study for such a degree is usually three to five years and the completed degree is usually designated as a Bachelor of Engineering, though some universities designate the degree as a Bachelor of Science. The degree generally includes units covering physics, mathematics, project
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management, design and specific topics in civil engineering. Initially such topics cover most, if not all, of the sub-disciplines of civil engineering. Students then choose to specialize in one or more sub-disciplines towards the end of the degree. While an Undergraduate (BEng / BSc) Degree will normally provide successful students with industry accredited qualification, some universities offer postgraduate engineering awards (MEng / MSc) which allow students to further specialize in their particular area of interest within engineering.
In most countries, a Bachelor's degree in engineering represents the first step towards professional certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience and exam requirements) before being certified. Once certified, the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa), Chartered Engineer (in most Commonwealth countries), Chartered Professional Engineer (in Australia and New Zealand), or European Engineer (in much of the European Union). There are international engineering agreements between relevant professional bodies which are designed to allow engineers to practice across international borders.
The advantages of certification vary depending upon location. For example, in the United States and Canada only a licensed engineer may prepare, sign and seal, and submit engineering plans and drawings to a public authority for approval, or seal engineering work for public and private clients. This requirement is enforced by state and provincial legislation such as Quebec's Engineers Act. In other countries, no such legislation exists. In Australia, state licensing of engineers is limited to the state of Queensland. Practically all certifying bodies maintain a code of ethics that they expect all members to abide by or risk expulsion. In this way, these organizations play an important role in maintaining ethical standards for the profession. Even in jurisdictions where certification has little or no legal bearing on work, engineers are subject to contract law. In cases where an engineer's work fails he or she may be subject to the tort of negligence and, in extreme cases, the charge of criminal negligence. An engineer's work must also comply with numerous other rules and regulations such as building codes and legislation pertaining to environmental law.
1.4. Careers
There is no one typical career path for civil engineers. Most people who graduate with civil engineering degrees start with jobs that require a low level of responsibility, and as the new engineers prove their competence, they are trusted with tasks that have larger consequences and require a higher level of responsibility. However, within each branch of civil engineering career path options vary. In some fields and firms, entry-level engineers are put to work primarily monitoring construction in the field, serving as the «eyes and ears» of senior design engineers; while in other areas, entry-level engineers perform the
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