查看完整版本: 自然界的纳米结构和现象,Nanostructures in Nature

自然界的纳米结构和现象,Nanostructures in Nature

[review=nanost-admin]很好的主题，自然界的现象确实很有趣，这样的研究目前也确实比较热，欢迎大家参与
)V5oCO? Y5F'f 该贴属于本论坛首发，专题请注明来自纳米科技世界论坛，谢谢！[/review]1f*d(Yr-}v8? yk$d
[align=center][b][size=5][font=黑体]自然界的纳米结构和现象[/font][/size][/b]
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自然界存在大量的奇妙形状的纳米结构，这些纳米结构可能为科学家构造纳米结构和认识自然界提供一种新的途径，欢迎大家收集这方面的信息。[/b]*nr s3^y^T
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sKeAa{ If we look closely, we can notice that many plants and animals around us have developed special features that are at the nanoscale level. Let's examine some of the ways in which nature has used nanostructures.  wI NJi;iM.Q
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d.@:iJP#]lp,X A moth’s eye has very small bumps on its surface. They have a hexagonal shape and are a few hundred nanometers tall and apart. Because these patterns are smaller than the wavelength of visible light (350-800nm), the eye surface has a very low reflectance for the visible light so the moth’s eye can absorb more light. The moth can see much better than humans in dim or dark conditions because these nanostructures absorb light very efficiently.  In the lab, scientists have used similar man-made nanostructures to enhance the aborption of infra-red light (heat) in a type of power source ( a thermo-voltaic cell) to make them more efficient ! Y
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7dk7z1rk On the  surface of a butterfly’s wings are multilayer nanoscale patterns. These structures filter light and reflect mostly one wavelength, so we see a single bright color. For instance the wings of the male Morpho Rhetenor appear bright blue. But the wing material is not, in fact, blue; it just appears blue because of particular nanostructures on the surface.  More precisely, the nanostructures on the butterfly’s wings are about the same size as the wavelength of visible light and because of the multiple layers in these structures optical interferences are created. There is constructive interference for a given wavelength (around 450nm for the Morpho Rhetenor) and destructive interferences for the other wavelengths, so we see a very bright blue color.  In the laboratory, many scientific instruments use this same phenomena to analyze the color of light.
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K,gPj#Y@Wc The edelweiss (Leontopodium nivale) is an alpine flower which lives at high altitudes, up to 3000m / 10,000 ft, where UV radiation is strong. The flowers are covered with thin hollow filaments that have nanoscale structures (100-200nm) on their periphery. They will absorb ultraviolet light, which wavelength is around the same dimension as the filaments, but reflect all visible light. This explains the white color of the flower. Because the layer of filaments absorbs UV light, it also protects the flower’s cells from possible damage due to this high-energy radiation.
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[b]甲壳虫上的纳米结构-1:[/b]
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[size=5][b]Beetle perfects artificial opal growth[/b][/size]
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[b]Researchers at the University of Oxford, UK, have discovered what they say is the first example of an opal-type photonic crystal structure in an animal. The intricate three-dimensional structure occurs in a small beetle just a few centimetres long. If the beetle’s self-assembly process can be emulated, the team says it could lead to a simpler and cheaper way of producing artificial opals (Nature 426 786).[/b]n J%G!o LG8h

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-s]5Z!V7SPFx;~ [i]An anterior view of the weevil Pachyrhynchus argus, a small beetle found in forests in north-eastern Australia. Its body appears a metallic green colour from all angles thanks to a photonic crystal structure that resembles opal. (Credit: Andrew Parker)[/i]
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“The interesting thing is that this has been found in a living organism,” said researcher Andrew Parker. “This means that the beetle must have cells that are making the structure, which gives us something to copy. There is a whole manufacturing process going on which starts with a series of chemicals and ends with a perfect opal structure.”
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%NS)Q mRAOh The opal-making animal is the weevil Pachyrhynchus argus, a small beetle found in forests in north-eastern Australia. Its body appears a metallic green colour from all angles thanks to a photonic crystal structure that resembles opal.Nc2N|/a:?

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[i]An SEM image of the scales which occur in patches over the beetle’s body. (Credit: Andrew Parker)[/i]T-rp4OJ*F
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The vivid colour comes courtesy of thin, flat scales which occur in patches over the beetle’s body. The scales consist of an outer shell and an inner structure that contains layers of 250 nm diameter transparent spheres.'Doq"Q^C:O

|5Eow*\5Q| “The spheres are arranged in hexagonal-close packing order,” explained Parker. “The scales contain the opal structure. There are tens of layers packed on top of each other in a single scale.”bM
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[i]An SEM of the opal structure that occurs inside the scales. The scale's inner structure contains tens of layers of 250 nm diameter transparent spheres arranged in hexagonal-close packing order. (Credit: Andrew Parker)
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Bu3[FBj'xc The scales produce the green colour by thin-film reflection. “Because we have stacks of spheres instead of flat layers, we have a three-dimensional structure where you can effectively form layers in many directions,” he said. “The reflections from each of these layers are superimposed and you get a colour-averaging effect which appears green.”
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;p3~:Kb1x [b]甲壳虫上的纳米结构-2:[/b]
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{@4G*p ]W#P 全文介绍见本论坛
1wkf"x,Hn#{%q [url=http://www.nanost.net/bbs/viewthread.php?tid=8943&highlight=Beetles%2Bturn%2Bto%2Bnanotechnology]http://www.nanost.net/bbs/viewthread.php?tid=8943&highlight=Beetles%2Bturn%2Bto%2Bnanotechnology[/url]
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&nK(P/`T1g [size=5]Nanostructured surface mimics Namib desert beetle[/size]P._ c}3[*\ o0G9[b9fC
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[b]Researchersat the Massachusetts Institute of Technology (MIT), US, have copied thestructure of a beetle's wings to make surfaces withhydrophilic/superhydrophobic patterning. The artificial surfaces couldhave applications in water harvesting, controlled drug release,open-air microchannel devices and labs-on-a-chip.[/b][-WNq8uO

-q qN1G:E'?~D-g Theresearchers read about the beetle's wings in a paper in Nature in 2001."If you sat at your desk and tried to just think of ways to do things,it would take a very long time," said Robert Cohen of MIT. "Once yousee these things in action, it's obvious what you have to do." Otherscientists have used bio-mimicry to recreate the superhydrophobicproperties of the Lotus leaf.| C.\
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The Stenocara beetle, which livesin Africa's Namib desert, uses its wings to capture moisture from themorning fogs that are the most reliable source of water in the region.The fog is so light that normal condensation can't take place.'k+G#x6F7o#HN

h"J,wkUr:Du Theinsect angles its wings forwards and upwards into the wind. Waterdroplets in the fog coalesce onto hydrophilic bumps about 100 µm indiameter on the wing surfaces. Eventually the droplets become so heavythat they pull away and roll down the surrounding hydrophobic surfaceareas of the wing to the beetle's mouth.T LHkjy4^9b6km

^`&L8d\i To create theirartificial structures, Robert Cohen, Michael Rubner and colleaguesfirst made superhydrophic coatings by decorating microporouspoly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA)microstructures with PAH/silica nanoparticles. They coated theresulting rough surface with a hydrophobic network of semi-fluorosilanemolecules.
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Next the researchers created hydrophilic regions byadding droplets of polyelectrolytes such as poly(acrylic acid) orpoly(fluorescein isothiocyanate allylamine hydrochloride) (FITC-PAH) ina water/2-propanol solution. The team believes that these chargedpolymer chains formed electrostatic bonds with the PAH or nanoparticlesof the substrate while parts of the chain remained on the surface,changing its wetting properties.
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n;l,V3|j[5N8M When such a structureincorporating 750 µm diameter hydrophilic spots of PAA was sprayed witha fine mist of water, it caused the droplets to aggregate together atthe hydrophilic regions. According to the scientists, the hydrophilicpatterns could be created using techniques such as inkjet printing,micropipetting and microcontact printing.cXjU p R

H-R%M&vR The team also modifiedthe superhydrophobic surfaces with charged small dye molecules such asmethylene blue and 2-propanol rose bengal in a solution ofwater/2-propanol. Adding the dye molecules made regions of the surfacehydrophilic but, unlike for the larger polyelectrolyte modifiers,washing the structure with water removed dye molecules from its surfaceand restored the original superhydrophobic state.&b5V$Vkk-oKS
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But some dyemolecules remained trapped inside the microstructure where water wasunable to reach them due to the superhydrophobic surface. The only wayto remove this dye was by rendering the surface hydrophilic with a PAAwater/2-propanol solution before washing with water. This techniquecould have applications in drug storage and controlled release.
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Theteam was able to make superhydrophilic canals by applyingsuperhydrophilic multilayers onto hydrophilic stripes on thesuperhydrophobic surface. Such structures could have applications inmicrofluidic devices.
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The researchers reported their work in [url=http://dx.doi.org/10.1021/nl060644q][i]Nano Letters[/i] [b]6[/b] 6 1213[/url].[/quote]

[b]蝴蝶身上的纳米结构[/b].Sh|5ek-U
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[size=5]Butterfly images take flight[/size]
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Y [b]Researchers at Oak Ridge National Laboratory, US, and North Carolina State University, US, have used scanning probe microscopy (SPM) to look at the structure of a butterfly's wing. They found that acoustic imaging enabled them to look at the internal structure of the wing in fine detail.[/b]
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9R0H%v L'r mpeo [i]Imaging butterflies[/i]
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Ho-C.Gt "The butterfly wing is extremely delicate and fragile, so measuring its mechanical and electromechanical properties by conventional techniques is virtually impossible," Sergei Kalinin of Oak Ridge National Laboratory told nanotechweb.org. "SPM provides the tool that can study these properties even in soft materials."VF"p3w:cD1k r

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RpX;r Kalinin and colleagues Alexei Gruverman and Brian Rodriguez of North Carolina State looked at the wings of the American Lady butterfly (Vanessa virginiensis). They modified a commercial microscope to carry out their atomic force acoustic microscopy measurements. q+Z@*I8h5rP#@
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"To our surprise, we found that acoustic imaging allows us to image much finer details of the internal structure of the biological system than we believed possible," said Kalinin. "The topographic image clearly shows the mesh structure, which enables high mechanical stability and rigidity of the wing. However, no details smaller than around 100 nm can be seen."
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~y+^H-hh%^+RE Acoustic imaging, on the other hand, revealed details of around 5 nm. The researchers say this is on the length scale of individual chitin fibrils forming the wing.
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|S4u G'Q0oq` "In a sense, now we can study mechanical properties on the level of single structural elements forming the biological tissues, eg chitin rods in insects, hydroxyapatite crystals in teeth and bones," said Kalinin. "This will allow us to visualize and understand the effects of diseases such as caries or osteoporosis on hard tissues, and formulate optimal strategies for drug and physical therapies." btB5Fw~
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Kalinin reckons that mechanical and electromechanical measurements on the cellular level could also provide new strategies for differentiating normal and cancer cells and investigating drug effects.j7F2qJ&a |
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The researchers would like to make their measurements quantitative, so that they can "say not only whether a particular region is softer or harder, but exactly how hard or soft it is".
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3Rl G E}$^I&T[x They'd also like to achieve higher resolution. "It is great to be able to probe elasticity on the 10 nm scale," said Kalinin, "but can we probe elasticity on the 1 nm or atomic scale? In other words, can we probe a single molecule inside the biological systems or a single unit cell in perovskite?"h1^5X#t*V
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Now the team is looking at SPM for probing electrical and electromechanical interactions in biological tissues. "This approach can be expected to provide novel insight into phenomena such as bone growth and remodelling, and muscular activities," said Kalinin. "Currently, we are exploiting the SPM approach to address problems such as cell development or protein imaging."$U3v4g/e7v,llO4H

o%|qX4J |"K9^ SOurce: nanotechweb.org.
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[b]蚊子的(腿)纳米结构：[/b],|~"T l9A3b
全文介绍见本论坛 :hand  [url=http://www.nanost.net/bbs/thread-11064-1-1.html]http://www.nanost.net/bbs/thread-11064-1-1.html[/url]r#iJ| f)eN/f^3Ty
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[size=5][align=center]Lotus effect shakes off dirt[/align][/size]+Bk;I4AI2UQ#]

-~r1b Td)f"^ [b]The lotus - a flowering wetland plant native to Asia - may not, at first glance, be of interest to the nanotechnologist. But researchers at German chemical company BASF are developing a spray-on coating that mimics the way lotus leaves repel water droplets and particles of dirt.[/b].h\ R DP$M
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z)u)]3~3~3a)\!E Lotus plants have superhydrophobic surfaces: water droplets falling onto them bead up and, if the surface slopes slightly, will roll off. As a result, the surfaces stay dry even during a heavy shower. What's more, the droplets pick up small particles of dirt as they roll, so that the lotus leaves are self-cleaning.
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.Y&s;b&^r/mhQ [i]A water droplet on the leaf of the Asiatic crop plant Colocasia esculenta absorbs particles of dirt as it rolls. In this picture taken by Barthlott's research team, we can also see the papillae on the cuticula. These papillae about 5 to 10 micrometres high are themselves coated by a fine nanostructure of wax crystals.[/i]
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gRvF}P Wilhelm Barthlott, a botanist from the University of Bonn in Germany, first explained the phenomenon and now owns a patent and the Lotus Effect trademark. The effect arises because lotus leaves have a very fine surface structure and are coated with hydrophobic wax crystals of around 1 nm in diameter. Surfaces that are rough on a nanoscale tend to be more hydrophobic than smooth surfaces because of the reduced contact area between the water and solid. In the lotus plant, the actual contact area is only 2-3% of the droplet-covered surface.x _Sxk&QZ

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v5pM _o The nanostructure is also essential to the self-cleaning effect - on a smooth hydrophobic surface, water droplets slide rather than roll and do not pick up dirt particles to the same extent.
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u+eT&i,} r7ehK [i]Water droplets on a wood surface treated with BASF's "Lotus Spray", which has made the surface extremely water-repellant (superhydrophobic).[/i]
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BASF's lotus-effect aerosol spray combines nanoparticles with hydrophobic polymers such as polypropylene, polyethylene and waxes. It also includes a propellant gas. As it dries, the coating develops a nanostructure through self-assembly. BASF says that the spray particularly suits rough surfaces such as paper, leather, textiles and masonry: the self-cleaning shoe may soon be a reality.!U~V8wLAO
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That said, in its current form, the spray may affect the colour of dark surfaces as its layers are slightly opaque. The coating can also be mechanically unstable on smooth surfaces. But BASF is working to overcome these problems. The company even aims to develop a product that will retain its lotus effect after abrasion with sandpaper. Dubbed lotus stone, the material has potential for use in the construction industry, in applications such as facing tiles.
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VN p6El0b*\0r Source:  nanotechweb.org.

[size=5][align=center]Turning the lotus effect on its head[/align][/size]+yH]Q:\.o,^$K
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[b]Companies that make water-repellent paints, fabrics and windscreens for cars often look to the lotus leaf for inspiration. The leaf is a symbol of purity in many cultures because of its ability to remain clean: when rain falls onto a lotus leaf, the drops of water that form on the surface roll off, taking any dirt with them. However, two researchers in the US have now discovered that although lotus leaves are superhydrophobic as far as droplets of water are concerned, they are actually hydrophilic with respect to condensed water vapour (Y-T Cheng and D Rodak 2005 Appl. Phys. Lett. 86 144101).[/b]Aj8tV#GY!]"a2s

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[i]Figure 1 Close-up of a lotus leaf, an example of a super-hydrophobic plant. The roughness of the leaf surface results from the coexistence of micron-sized bumps and nanoscale hair-like structures. (Image credit: W Barthlott)[/i]"_5G@;__^&|)RB{&A n V

4D'G!UY6{Ud6_o Microscope observations reveal that the waxy surface of the lotus leaf is made of micron-sized bumps that, in turn, are covered with nanoscale hair-like tubes (figure 1). This two-fold structure traps air under any rain drops that fall on the leaf, creating a surface that efficiently repels water. However, experiments on this so-called lotus-effect have only focused on how millimetre-sized droplets behave when they encounter the leaf's surface.
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1oY9[FR5oOi7X;pQu Figure 2 Schematic illustrations of water drops on lotus leaf following water condensation: (a) a water drop on an area with a small amount of condensed water, and (b) on an area with a large amount of condensed water (Image credit: Appl. Phys. Lett. 86 114101).[/i] `[vZ$|
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H(KT~Bpk Yang-Tse Cheng at General Motors Research and Development Center in Michigan and Daniel Rodak of Ricardo Meda Technical Services, also in Michigan, began by placing a lotus leaf above a source of water vapour. After just a few minutes the water began condensing onto the leaf in small droplets. Moreover, as condensation continued, some of these droplets merged to form bigger drops that remained on the surface of the leaf - contrary to what was expected.U%y$~yQ W-uMe

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Cheng and Rodak say the droplets become trapped between the nano-scale hairs on the leaf. The drops then coalesce with other drops and eventually begin to fill the cavities created by the micron-sized bumps (figure 2). Moreover, any new drops falling onto the leaf can then stick to it, making the surface hydrophilic rather than hydrophobic (figure 3).
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"The question now is whether truly superhydrophobic surfaces can exist," says Cheng. "Condensation experiments like ours are crucial to understanding the wetting behaviour of surfaces and should be included in any standard evaluation of hydrophobic materials."^)c3lA ?

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Source:  PhysicsWeb.

图片很不错哦！大有用处

哇，太好了，自然界漫长的进化真是不简单啊

怎么都是昆虫的？期待有人帖出更多精彩的图片