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从苍蝇的眼睛来看纳米生物学

[b][size=4]The eye of the fly - just one of many inspiring biomodels for nanotechnology[/size][/b]S)v9F2K2b2K
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:nst Looking at Nature as a successful design lab with millions of years of research experience, it is quite surprising that scientists haven't tried harder to copy some of Nature's more successful and impressive design blueprint. The list of actual commercialized biodesign-inspired products is very short. The most famous is Velcro, the hook-loop fastener that was invented in 1945 by Swiss engineer, George de Mestral. The idea came to him after he took a close look at the burrs (seeds) of burdock which kept sticking to his clothes and his dog's fur on their daily summer walks in the Alps. He examined their condition and saw the possibility of binding two materials reversibly in a simple fashion. And then, of course, there are the Wright Brothers, who modeled their planes on the structure of bird wings. Today, there are quite a number of terms such as bionics, biomimetics, biognosis, biomimicry, or even 'bionical creativity engineering' that refer to more or less the same thing: the application of methods and systems found in Nature to the study and design of engineering systems and modern technology. The use of design concepts adapted from Nature is a promising new route to the development of advanced materials and increasingly nanotechnology researchers find nanostructures a useful inspiration for overcoming their design and fabrication challenges. Because biological structures are the result of hundreds of thousands of years of evolution, their designs possess many unique merits that would be difficult to achieve by a complete artificial simulation. However, utilizing them as biotemplates and converting them to inorganic material could be a highly reproducible and low-cost process for fabricating complex nanostructures with unique functions. Complex functional systems are still out of reach but the replication of biological structures is making good progress. A recent example is the fabrication of antireflection nanostructures by replicating fly eyes.N#z;T[`c4yv
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[color=red]There are a number of Spotlights on this fascinating topic of nanotechnologists playing catch-up with nature(as see following postes): "Nature's bottom-up nanofabrication of armor", "Nanotechnology inspired by mussels and seashells" or "Algae shells: one example how nanotechnology is trying to copy Mother Nature", or "Unlocking nature's protein material concepts enables tomorrow's nanotechnology materials and cures", to name just a few.[/color]
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Insects have a lot of unique capabilities. A number of nanotechnology researchers are trying to duplicate these natural structures in order to achieve superior and unusual functionalities in man-made materials and devices. The biotemplated fabrication of natural biological structures is an approach for receiving unique nanostructures that cannot be made using conventional nanofabrication techniques, such as lithography."h0r:@'@3W2q$p+Y5i

l[\'g#N4Y!FX Dr. Zhong Lin Wang, Regents' Professor, COE Distinguished Professor, and Director, Center for Nanostructure Characterization, at Georgia Tech, already has experience with bioinspired fabrication. We have covered his work in our Spotlight series before, most recently with a report on a direct-current nanogenerator that is driven by ultrasonic waves (Nanoscale power plants).
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r2\_%kg$euV#~qz In 2006, Wang and his group replicated butterfly wings ("[url=http://dx.doi.org/doi:10.1021/nl061851t]Controlled Replication of Butterfly Wings for Achieving Tunable Photonic Properties[/url]").:Z1LJ/x*E ~B.R

m7N+LRR Now, Wang's lab has examined the fine structure of the compound eyes of a household fly and precisely replicated its entire structure using a low-temperature atomic layer deposition technique. The results have been published in the December 6, 2007 online edition of Nanotechnology ("[url=http://dx.doi.org/doi:10.1088/0957-4484/19/02/025602]Bio-inspired fabrication of antireflection nanostructures by replicating fly eyes[/url]").!pO!O*z,TH z
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"Our contribution is the ability to replicate a biological structure and then measure its physical properties and find out why a particular structure exhibits unusual properties" Wang explains to Nanowerk. "By doing so, we are trying to find an effective fabrication path that follows the evolution of Nature for making extraordinary nanostructures."
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"The surface of the fly eye is covered by highly packed protuberances, which potentially increases visual efficiency through increased photon capture for a given stimulus" Wang comments on his group's most recent bioinspired nano research. "We carefully examined the fine structure of the household fly compound eye and then completely replicated the entire configuration by alumina through a low-temperature atomic layer deposition process."e?Q!w\/M

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[color=dimgray]Mosquito eye (Image: Raija Peura, University of Oulu Institute of Electron Optics' Image gallery)[/color]
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Insects have compound eyes – instead of one lens they see through a sphere with many hundreds or thousands of eyes, so called ommatidiums. Household flies, for instance, have a very well-developed visual system with the capacity of seeing motion, color and pattern of objects in their environment due to their advanced compound eyes.E1HR{6R}
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The Georgia Tech scientists' goal has been focused on the optical properties of the fly eye's nanostructure, aiming to understand the visible light, UV light and infrared light transmission through the structures.
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/B*m+J-KAE*O "We achieved the alumina replica by removing the fly compound eye template at high temperature, and the alumina coating was crystallized simultaneously" Wang describes the experimental details. "The success of our replication was not only with the morphologies but also with the optical features – the unique antireflection property of the eye was also inherited by the alumina replica. By measuring the reflective spectra of the replica, we demonstrated that the alumina replica of a fly eye was an efficient antireflection structure of visible light at an incident angle up to 80°."C9X#[IB8Z1w
Wang says that the fly eye replica with antireflection structure exhibits great potential in the applications of optical coating, sensing or lens arrays. His group is now working on developing more sophisticated replication techniques for tuning the optical response of the structure in order to optimize the performance.w%ZM6iT
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[[i] 本帖最后由 nano 于 2008-01-02 20:21 编辑 [/i]]

[size=4][b]Nature's bottom-up nanofabrication of armor[/b][/size]~9o#ll'C6Nv(T3c

qTi;k.?"i X :nst Seashells are natural armor materials. The need for toughness arises because aquatic organisms are subject to fluctuating forces and impacts during motion or through interaction with a moving environment. Nacre (mother-of-pearl), the pearly internal layer of many mollusc shells, is the best example of a natural armor material that exhibits structural robustness, despite the brittle nature of their ceramic constituents. This material is composed of about 95% inorganic aragonite with only a few percent of organic biopolymer by volume. New research at the university of South Carolina reveals the toughening secrets in nacre: rotation and deformation of aragonite nanograins absorb energy in the deformation of nacre. The aragonite nanograins in nacre are not brittle but deformable. The new findings may lead to the development of ultra-tough nanocomposites, for instance for armor material, by realizing the rotation mechanism.+uNS5L#gKK
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Super-tough and ultra-high temperature resistant materials are in critical need for applications under extreme conditions such as jet engines, power turbines, catalytic heat exchangers, military armors, aircrafts, and spacecrafts. Structural ceramics have largely failed to fulfill their promise of revolutionizing engines with strong materials that withstand very high temperature. The major problem with the use of ceramics as structural materials is their brittleness. Although many attempts have been made to increase their toughness, including incorporation of fibers, whiskers, or particles, and ZrO2 phase transformation toughening, currently available ceramics and their composites are still not as tough as metals and polymers. The brittleness of ceramic materials has not yet been overcome. It has proven difficult to solve this problem by conventional approaches.N u iGJxry

*J5y1mb L On the other hand, Nature has evolved complex bottom-up methods for fabricating ordered nanostructured materials that often have extraordinary mechanical strength and toughness. One of the best examples is nacre. It has evolved through millions of years to a level of optimization not currently achieved in engineered composites.
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This material has a brick-and-mortar-like structure with highly organized polygonal aragonite platelets of a thickness ranging from 200 to 500 nm and an edge length about 5 µm sandwiched with a 5-20 nm thick organic biopolymer interlayer, which assembles the aragonite platelets together. The combination of the soft organic biopolymer and the hard inorganic calcium carbonate produces a lamellar composite with a 2-fold increase in strength and a 1000-fold increase in toughness over its constituent materials.
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Such remarkable properties have motivated many researchers to synthesize biomimetic nanocomposites that attempt to reproduce nature’s achievements and to understand the toughening and deformation mechanisms of natural nanocomposite materials.
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Pm&C7WJ9c;k l Dr. Xiaodong Li, who heads the Nanostructures and Reliability Laboratory at the University of South Carolina, and his team have published two papers that examine the role of nanostructures in the amazing properties of nacre. In a first paper (" [url=http://dx.doi.org/doi:10.1021/nl049962k]Nanoscale Structural and Mechanical Characterization of a Natural Nanocomposite Material: The Shell of Red Abalone[/url]"), the group reported the discovery of nanosized grains (particles) in nacre. However, the functionality of these aragonite nanograins was entirely unknown. Subsequently, many research groups asked: What roles do the nanoscale structures play in the inelasticity and toughening of nacre? Can we learn from this to produce nacre-like nanocomposites?]9XPj
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In a recent follow-up paper, Li and his group now reveal the functionality of these aragonite nanograins. The paper is titled "[url=http://dx.doi.org/doi:10.1021/nl061775u]In Situ Observation of Nanograin Rotation and Deformation in Nacre[/url]", which appeared in the September 14, 2006 online edition of Nano Letters.
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"To reveal the secret recipe of nacre is not an easy job" Li explains his research to Nanowerk. "We developed a micro-mechanical tester that can be used inside an atomic force microscope. We performed tensile and bending tests on nacre in situ where the nacre surface was imaged simultaneously by the atomic force microscope. The discoveries – rotation and deformation of aragonite nanograins clarify the previous misunderstandings in modeling work, and provide a nanoscale modeling boundary condition. This opens up opportunities to develop nacre-like ultra tough materials."_3yS'k$i8M/r

Pg'mQvGb The grain rotation and deformation mechanisms in nacre aragonite platelets can be summarized by this figure:"T$@(l0iX(Fj-[

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q1gJ\&W(RW0R [color=gray]With no external applied strain/stress, nanograins with irregular shapes are originally packed very closely by the biopolymer adhesives to form a robust structure (as shown in a).~0X-u;as ?zK
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Upon tension, the biopolymer between the nanograins is stretched in the tensile direction, which allows enough space for certain grains to rotate. Since the shape of these nanograins is normally irregular, the rotation of individual nanograins will push their neighbor grains apart, thereby resulting in an increase in the spacing between the rotated nanograins and their neighbor grains (as shown in b).
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The spacing behavior between the nanograins within an aragonite platelet causes the aragonite platelet to expand in the direction perpendicular to that of the applied strain/stress.
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2s0ym&@*o Schematics of grain rotation and deformation mechanisms in an aragonite platelet. D denotes grain deformation. The blue arrows denote the tensile direction. Green arrows denote the rotation direction of grains.(Reprinted with permission from the American Chemical Society)
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The new findings are expected to revolutionize the way of preparing tough ceramic materials and structural components, and will open up new application opportunities of ceramic materials and other materials as well.7Sf k] [&C$TY)f

)`S4T4|5@)jA"eC%vN;[ Li points out that Nature has long been using bottom-up nanofabrication methods to form self-assembled nanomaterials that are much stronger and tougher than many man-made materials formed top-down.
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P)f#] uG.@fy "Mother Nature knows best" Li says. "Nature has evolved highly complex and elegant mechanisms for materials design and synthesis. Living organisms produce materials with physical properties that still surpass those of analogous synthetic materials with similar phase composition. We need to turn our attention to Nature's designs and fabrication of materials. There is still a lot we need to learn from Nature."

[size=4][b]Native protein nanolithography that can write, read and erase[/b][/size][,n0d ~)h0Wla
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:hand [url=http://www.nanost.net/bbs/viewthread.php?tid=5923&highlight=Native%2Bprotein%2Bnanolithography]:nst [/url]

[b][size=4]Algae shells: one example how nanotechnology is trying to copy Mother Nature[/size][/b]
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:hand [url=http://www.nanost.net/bbs/viewthread.php?tid=1566&highlight=Algae%2Bshells]:nst [/url]

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谢谢分享！！

[b][size=4]Unlocking nature's protein material concepts enables tomorrow's nanotechnology materials and cures[/size][/b]%D@:Ap5t1F9mDR
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[[i] 本帖最后由 nano 于 2008-01-02 20:35 编辑 [/i]]

好铁，赞～～
~@#pD0S,h9@ @I :good1 :good1

很好看的图片:victory:

good!~ding yi ge !~

qiang zzzzzzzzz

:Q :funk: M#[R^3l'mh,}
nice paper

好东西啊，谢谢版主啦！！！

真心感谢楼主的分享！:handshake

很有意思！

文章很长啊！！！！！