Stories tagged self assembly

Growing computers with DNA

Scientists from California Institute of Technology and IBM have for the first time coaxed components made from DNA to self organize in a way that could serve as a template upon which additional components like wires and switches could attach.

This technique, which "grows" nano circuits rather than "tooling" them, could result in smaller circuits and save millions of dollars.

Learn more at SiliconValley.com:
IBM scientists take big step toward DNA microchips

Jun
29
2008

Nano structure self assembly
Nano structure self assemblyCourtesy Scott Warren and Uli Wiesner, Cornell University

Materials scientists perfect nano assembly of catalytic meshes

Catalysts, because of its shape, can speed up chemical reactions. Platinum is a useful catalyst in fuel cells but because it costs over $2000 an ounce, it needs to be used efficiently. One way to maximize the effectiveness of platinum is to maximize its surface area.

Cornell researchers have developed a method to self-assemble metals into complex configurations with structural details about 100 times smaller than a bacterial cell by guiding metal particles into the desired form using soft polymers. NSF News

How to self-assemble porous nano mesh

To keep nano spheres of platinum from clumping or "globbing" they are coated with an organic material known as a ligand. The innovative use of the ligands allows for the metal nanoparticles to be dissolved in a solution containing long co-polymer chains, or blocks, of molecules linked together to form a predictable pattern. After the spheres have filled in the spaces created by the co-polymer chains, heat is applied until the polymer turns to a carbon scaffold. The scaffold holds the platinum spheres in place until cooled. The carbon is then dissolved away leaving an intricate hexagonal mesh of platinum (see image above).

New surface textures will benefit plasmonics science

These metalic surfaces will also be of interest to scientists working in an area called plasmonics. Plasmonics is the study of interactions among metal surfaces, light, and density waves of electrons, known as plasmons. Improved optics applications, like lasers, displays, and lenses and better transmission of information within microchips will be some benefits.

Feb
05
2008

Nano (not!): Built for the 1958 Brussels World's Fair, this model of a body-centred cubic crystal is similar to the nano crystal created with DNA except it is magnified 165 billion times.
Nano (not!): Built for the 1958 Brussels World's Fair, this model of a body-centred cubic crystal is similar to the nano crystal created with DNA except it is magnified 165 billion times.Courtesy John Kerno

First step toward three-dimensional catalytic, magnetic, and/or optical nanomaterials

Assembling structures that are 1000 times smaller than a human hair is difficult. One technique that works is known as "self assembly". A random mixture of microscopic parts can be coaxed into assembling spontaneously into a desired structure by attaching appropriate segments of DNA to various parts. Complementary DNA strands want to "pair up". This is how nano structures are assembled in living organisms.

"researchers at the U.S. Department of Energy's Brookhaven National Laboratory have for the first time used DNA to guide the creation of three-dimensional, ordered, crystalline structures of nanoparticles.

Nanomaterials: Golden handshake

The team from Brookhaven and another group from Northwestern University in Evanston, US, both started with tiny spheres of gold around 10 nanometres across, and attached short strands of DNA. By varying the length of the DNA strands, their flexibility,and the types of sticky ends, they are working toward reliably binding them together in particular ways. This is the first step toward building three-dimensional catalytic, magnetic, and/or optical nanomaterials.

Sources:

Jun
15
2006

Marine sponge glass: photo by Art Oglesby; Glass structure formed by marine sponge.
Marine sponge glass: photo by Art Oglesby; Glass structure formed by marine sponge.

One approach to creating devices on a molecular scale is to have such devices self-assemble similar to the way living things "grow".
David E. Morse is attempting to mimic how living organisms self-assemble complex shapes with nanoscale precision. The intricate glass structure pictured was assembled molecule by molecule by a species of marine sponge. The genes responsible for the glass structures encode for enzymes that serve as both a physical template for the structure and a catalyst for assembling molecular precursors into the desired material.

Morse and his colleagues begin with a solution of molecular precursors. The researchers then expose the solution to ammonia vapor, which, as it slowly diffuses into the solution, acts as a catalyst. The physical template for the material is the surface of the solution. At this surface, where the vapor concentration is greatest, the material forms a thin film.

"At first the crystals form at the [surface], but with time they begin to project down into the solution like stalactites growing down from the roof of a cave," Morse says. "What you end up with is a nanostructured thin film of semiconductor with very high surface area because of all the projecting thin plates or needles that project down into the solution. We are accessing structures that in some cases had never been achieved before. And in some cases we're discovering electronic properties that had never been known before for that class of materials," says Daniel Morse, professor of molecular genetics and biochemistry at UCSB, who led the project. The method works with a wide variety of materials. So far, he says, the group has made "30 different kinds of oxides, hydroxides, and phosphates."

Source article; Technology Review
A list of selected publications by Morse.

May
15
2006


Self-assembling lattices: credit-Nature TEM images of the characteristic projections of the binary superlattices, self-assembled from different nanoparticles, and modelled unit cells of the corresponding three-dimensional structures.

Computers use disks coated with magnetic particles to remember data in binary form (0's & 1's). Manufacturers squeeze more memory into these disks by making smaller and smaller magnetic particles. Packing these ever smaller particles in an orderly way is the challenge. Recently scientists have coaxed molecular sized particles to self assemble into orderly lattices.

Natural attractions and repulsions that prompt molecules to form intricate patterns (like snowflakes) can build useful structures--say, medical implants or components in electronic chips. Nanocrystals, a benchmark material for nanotechnology, are one-billionth of a meter in size and are carefully manufactured by the millions in labs, explains Stephen O'Brien, assistant professor of applied physics and mathematics. Together with researchers at IBM, he and his research team at Columbia University have demonstrated that you can design small regions of magnetic and semiconducting nanocrystals that will assemble into a new and unique material.
Stephen O'Brian explains the process of self-assembly in a video. (click this for Real or Quicktime links)

More than 15 different structures, using combinations of semiconducting, metallic and magnetic nanoparticle building blocks are described in their paper published in Nature Magazine(Nature 439, 55-59 (5 January 2006) | doi:10.1038/nature04414). At least ten of these colloidal crystalline structures have not been reported previously.

Columbia News article

Nature article summary

IBM nano research projects