Mostrando entradas con la etiqueta Nanoestructuras. Mostrar todas las entradas
Mostrando entradas con la etiqueta Nanoestructuras. Mostrar todas las entradas

jueves, 23 de mayo de 2013

These Self-Assembling Nanoflowers Are As Beautiful As They Are Tiny

ORIGINAL: PopSci
05.22.2013

Harvard researchers grew these lovely microscopic gardens using delicate chemical reactions.

Nanoflower 4 Wim L. Noorduin
A nanorose may not smell as sweet as an organic one, but the red petals on this micron-scale flower are unquestionably just as beautiful. At Harvard University, materials scientists have perfected an underwater chemical reaction that results in these gorgeous, self-assembling nanoflowers.
The microscopic structures are crystals that build themselves, one molecule at a time, on a glass surface submerged in a beaker of water, barium chloride, and sodium silicate. When carbon dioxide from the air naturally dissolves in the water, it sets off the chemical reaction that causes the crystals to form.

Though the colors in these images are artificial, the intricate shapes of the nanoflowers are very real. The twists, curves, and ruffles are created when the scientists shift the components of the chemical reaction; the crystals naturally "grow" toward or away from various chemical gradients. For example, the broad-leaf shapes you'll see in the gallery formed in solutions with extra carbon dioxide.

"When you look through the electron microscope, it really feels a bit like you’re diving in the ocean, seeing huge fields of coral and sponges," says Wim L. Noorduin, a postdoctoral fellow at Harvard and lead author of the paper in Science. "Sometimes I forget to take images because it's so nice to explore."

Nanoflower Wim L. Noorduin
Nanoflower Wim L. Noorduin
Nanoflower Wim L. Noorduin
Nanoflower Wim L. Noorduin
Nanoflower Wim L. Noorduin







lunes, 11 de marzo de 2013

Insect wings shred bacteria to pieces

ORIGINAL: Nature
Trevor Quirk
04 March 2013

Antibacterial 'nanopillars' on cicada wings pull bacterial membranes apart.

Antibacterial 'nanopillars' on cicada wings pull bacterial membranes apart.
The veined wing of the clanger cicada kills bacteria solely through its physical structure — one of the first natural surfaces found to do so. An international team of biophysicists has now come up with a detailed model of how this defence works on the nanoscale. The results are published in the latest issue of the Biophysical Journal1.

The clanger cicada (Psaltoda claripennis) is a locust-like insect whose wings are covered by a vast hexagonal array of 'nanopillars' — blunted spikes on a similar size scale to bacteria (see video, bottom). When a bacterium settles on the wing surface, its cellular membrane sticks to the surface of the nanopillars and stretches into the crevices between them, where it experiences the most strain. If the membrane is soft enough, it ruptures (see video, top).

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Lead study author Elena Ivanova of Australia's Swinburne University of Technology in Hawthorne, Victoria, says that she was surprised that the bacterial cells are not actually punctured by the nanopillars. The rupturing effect is more like “the stretching of an elastic sheet of some kind, such as a latex glove. If you take hold of a piece of latex in both hands and slowly stretch it, it will become thinner at the centre, [and] will begin to tear,” she explains.

To test their model, Ivanova and her team irradiated bacteria with microwaves to generate cells that had different levels of membrane rigidity. Their hypothesis was that the more rigid bacteria would be less likely to rupture between the nanopillars. The results validated the model, but also demonstrated that the cicada’s nanopillar defence is limited to bacteria that have sufficiently soft membranes.

Further study of the cicada’s wing is needed before its physical-defence properties can be mimicked in man-made materials. Anne-Marie Kietzig, a chemical engineer at McGill University in Montreal, Canada, who was not involved in the study, suggests that materials based on this model could one day be applied to public surfaces that commonly harbour disease, such as bus railings. “This would provide a passive bacteria-killing surface,” she says, adding that it “does not require active agents like detergents, which are often environmentally harmful”.

Naturedoi:10.1038/nature.2013.12533

References


Pogodin, S. et al. Biophys. J. 104, 835–840 (2013).
ChemPort Hide context
…The results are published in the latest issue of the Biophysical Journal1in article

domingo, 23 de diciembre de 2012

Arbitrarily complex 3D DNA nanostructures built from DNA bricks


Computer-generated 3D models (top) and corresponding 2D projection microscopy images (bottom) of nanostructures self-assembled from synthetic DNA strands called DNA bricks. (Image Credit: Yonggang Ke, Wyss Institute, Harvard University.)
This past May we posted news of a major advance in the toolkit for DNA nanotechnology. Researchers led by Wyss Institute core faculty member Peng Yin developed a very versatile, rapid, and inexpensive way to assemble arbitrarily complex 150-nm two-dimensional DNA nanostructures from 42-nucleotide DNA tiles. A hat tip to ScienceDaily for reprinting this Wyss Institute news release of another major advance from the same research group aided by another Wyss Core Faculty member William ShihResearchers Create Versatile 3D Nanostructures Using DNA ‘Bricks’”:

Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have created more than 100 three-dimensional (3D) nanostructures using DNA building blocks that function like Lego® bricks — a major advance from the two-dimensional (2D) structures the same team built a few months ago.

In effect, the advance means researchers just went from being able to build a flat wall of Legos®, to building a house. The new method, featured as a cover research article in the 30 November issue of Science [abstract], is the next step toward using DNA nanotechnologies for more sophisticated applications than ever possible before, such as “smart” medical devices that target drugs selectively to disease sites, programmable imaging probes, templates for precisely arranging inorganic materials in the manufacturing of next generation computer circuits, and more. …

Earlier this year, the Wyss team reported in Nature how they could create a collection of 2D shapes by stacking one DNA brick (42 bases in length) upon another.

But there’s a “twist” in the new method required to build in 3D.

The trick is to start with an even smaller DNA brick (32 bases in length), which changes the orientation of every matched-up pair of bricks to a 90 degree angle — giving every two Legos® a 3D shape. In this way, the team can use these bricks to build “out” in addition to “up,” and eventually form 3D structures, such as a 25-nanometer solid cube containing hundreds of bricks. The cube becomes a “master” DNA “molecular canvas”; in this case, the canvas was comprised of 1000 so-called “voxels,” which correspond to eight base-pairs and measure about 2.5 nanometers in size – meaning this is architecture at its tiniest.

The master canvas is where the modularity comes in: by simply selecting subsets of specific DNA bricks from the large cubic structure, the team built 102 3D structures with sophisticated surface features, as well as intricate interior cavities and tunnels. “This is a simple, versatile and robust method,” says Peng Yin, Ph.D., Wyss core faculty member and senior author on the study.

The DNA-brick technique capitalizes on the ability of DNA strands to selectively attach to other strands, thanks to the underlying “recipe” of DNA base pairs. …

Another method used to build 3D structures, called DNA origami, is tougher to use to build complex shapes, Yin said, because it relies on a long “scaffold” strand of DNA that folds to interact with hundreds of shorter “staple” strands – and each new shape requires a new scaffold routing strategy and hence new staples. In contrast, the DNA brick method does not use any scaffold strand and therefore has a modular architecture; each brick can be added or removed independently.

We are moving at lightning speed in our ability to devise ever more powerful ways to use biocompatible DNA molecules as structural building blocks for nanotechnology, which could have great value for medicine as well as non-medical applications,” says Wyss Institute Founding Director Don Ingber, M.D., Ph.D.

The news release includes a video and an animation showing how the DNA strands self-assemble to build complex 3D objects.
Making Structures with DNA "Building Blocks" from Wyss Institute on Vimeo.

This powerful advance should lead to programmable molecular arrangements for several applications. Any of a great variety of molecular species can be attached to DNA bricks and thus assembled into arbitrarily complex 3D configurations. What sorts of molecular species would give DNA bricks functionality that could be used to build a very primitive nanofactory? Where does this advance stand on the road to molecular manufacturing or productive nanosystems? Back in May of 2005 Chris Phoenix and Tihamer Toth-Fejel authored a report for the NASA Institute for Advanced Concepts (“Large-Product General-Purpose Design and Manufacturing Using Nanoscale Modules“, PDF) in which they proposed two different designs for a very primitive nanofactory based upon planar assembly, each using 5-nm molecular building blocks of unspecified composition, prepared by either chemical synthesis or self-assembly, and incorporating a few simple functional capabilities. Certainly one or more functions could be attached to either these 2.5-nm DNA voxels or the 25-nm larger structures comprising 1000 voxels. Can anyone see a way from this advance to a primitive nanofactory that could be used to build improved nanofactories, leading eventually to molecular manufacturing? 
—James Lewis, PhD

This entry was posted on Thursday, December 6th, 2012 at 12:11 PM and is filed under Atomically Precise Manufacturing (APM),Bionanotechnology, Molecular Nanotechnology, Molecular manufacturing, Nano, Nanobiotechnology, Nanotech,Nanotechnology, Productive Nanosystems, Research. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

sábado, 1 de diciembre de 2012

Synopsis: The Blueprint for DNA Origami

ORIGINAL: Physics APS
J. M. Arbona et al., Phys. Rev. E (2012)


Jean Michel Arbona, Jean-Pierre Aimé, and Juan Elezgaray
Published November 21, 2012


DNA provides the code for life, but it also can be a construction material for self-forming nanostructures. So-called DNA origami takes advantage of the highly selective interactions between strands of DNA to make arbitrary two- and three-dimensional shapes. To help understand the potential of this nanotechnology, a group has generalized previous theoretical work that treats DNA as a “stack of plates. The adapted model, described in Physical Review E, is able to reproduce mechanical and elastic properties of DNA origami.

Researchers know how to synthesize strands of DNA that self-organize into ribbons, boxes, and other forms that may eventually be used as electronic templates and nanorobots. After being heated and then slowly cooled, the strands fold and weave together, controlled by the unique pairings between DNA bases. However, current models of DNA origami tend to approximate these base pair interactions by using an effective elastic theory for the connections between strands.

Jean Michel Arbona and his colleagues from the Institute of Chemistry and Biology of Membranes and Nano-objects (CBMN) in Pessac, France, have devised a new coarse-grain model that specifically accounts for base pair interactions. They assume each base pair is like a rigid ellipsoid, or “plate,” that swivels and tips with respect to its neighbors. This model was originally developed for “normal” double-stranded DNA, but Arbona and collaborators are now applying it to the multiple strands that intertwine in DNA origami. In addition to base pair interactions, the model includes the electrostatic repulsion coming from excess charge on the DNA molecule. Using Monte Carlo simulations, the team searched for stable configurations, which ended up reproducing DNA origami structures that have been observed in experiments. – Michael Schirber

martes, 7 de agosto de 2012

SLIPS liquid repeller is inspired by carnivorous plants, enemy to insects and graffiti artists alike

ORIGINAL: Engadget
Aug 3rd 2012 8:12PM


When a team of Harvard researchers wanted to create the ultimate liquid- and solid-repelling surface, they looked toward the Nepenthes pitcher plant, where curious insects check in and never check out, thanks to slippery walls that lead to their tiny, horrific fate. The tropical plant inspired the creation of SLIPS (Self-healing, Slippery Liquid-Infused Porous Surface), a synthetic material that utilizes nano/ microstructured substrates, capable of repelling just about anything you can throw at it. During a visit to the hallowed Crimson halls, the team was kindly enough to show off the material through a series of messy, messy demos, dropping water, motor oil, liquid asphalt and newly-mixed concrete on aluminum and glass. The team even went crazy with a can of black spray paint, comparing the results to a Teflon surface. The outcome was the same in all case -- an amazingly repellent material.

Nepenthes pitcher plant. This photo was taken at the San Francisco Conservatory of Flowers in Golden Gate Park. Mongabay.com ran an article on the Conservatory at Medicinal powers of plants explored at San Francisco Conservatory of Flowers 
The team has published a number of papers on the stuff, including ones that demonstrate its ice- and bacteria-repelling properties. Oh, and like its natural inspiration, SLIPS does a great jobs keeping bugs off its surface. You can check out our demos and one unhappy ant filmed by the SLIPS team. No insects were harmed in the making of our video, at least -- and the lab assures us that ant had a good life before learning the hard way why it shouldn't mess with Harvard scientists.



SLIPS