Water could be the key to cheaper nanoelectronics!

Previously we saw that water could play a role in enhancing the density of memory storage devices. (http://nanosciencetech.blogspot.com/2008/11/ultra-dense-memory-storage-devices.html).

Now a recent study at the Kavli Institute of Nanoscience in DELFT, Netherlands shows that a splash of the wet stuff could help make nanoelectronic manufacturing both quicker and cheaper.

Now days, nanoscale components are embedded in the electronic circuit boards, but they are very difficult and they require superior level of accuracy. To get complicated nanostructures nanostructures on a silicon chip it is sometimes necessary to grow them in separate layers and then transfer these one by one onto the final chip (PDF) to build them into working components.

Often it takes strong chemicals to separate the layers from the surface on which they are grown, and high temperatures may be needed to activate the thermal adhesives that keep the components in place at their destination.

Researchers have found a way to use water to transfer layers quickly and easily from one surface to another. They exploit the fact that different materials have different hydrophilicity defined by the tendency to attract water through transient hydrogen bonds.

The team took a relatively hydrophilic silicon wafer onto which a graphene structure had been deposited in the desired pattern. Then they dipped it into a solution containing a hydrophobic polymer that dried to form a strong, solid hydrophobic layer on top of the wafer.

Next, they submerged the silicon wafer in water. Because graphene is equally hydrophobic, the water molecules wiped out both layers out of the way to wet the hydrophilic silicon beneath it, gradually "wedging" them off the silicon base. The polymer-graphene film then floated to the surface of the water.

Now the team placed a second silicon wafer beneath the floating film and used a needle to prod the film into position before draining away the water. Intermolecular forces between the graphene and silicon then provide a surprisingly stable attachment.

They then dissolved away the hydrophobic polymer to leave the graphene attached to the new wafer. Repeating the technique several times would allow graphene layers to be built up into a complex electronic nanostructure.

WANDA: Reducing the Human Error!

Berkeley Lab scientists have established a revolutionary nanocrystal-making robot, capable of producing nanocrystals with extreme precision. This one-of-a-kind robot provides colloidal nanocrystals with custom-made properties for electronics, biological labeling and luminescent devices.

This robotic engineer is named WANDA (Workstation for Automated Nanomaterial Discovery and Analysis) and was developed in collaboration with Symyx Technologies at the Molecular Foundry, a U.S. Department of Energy User Facility located at Berkeley Lab. By automating the synthesis of these nanocrystals, WANDA overcomes the issues facing traditional techniques, which can be laborious and are difficult to reproduce from one laboratory to the next. What's more, WANDA's synthetic prowess can help researchers sift through a large, diverse pool of materials for specific applications. Such a combinatorial approach has been used for decades in the pharmaceutical industry and now is being applied to nanomaterials at the Foundry.

WANDA makes nanocrystals of exceptional quality - every time - optimized for different applications. It can also be used to discover new nanocrystal compositions with advantageous properties.

WANDA's liquid-handling robotics prepares and initiates reactions by injecting nanocrystal precursor chemicals into an array of reactors. After a series of reactions is complete, the structural and optical properties of these nanocrystals can be screened rapidly, also using automated methods. WANDA is kept inside a nitrogen-filled chamber, designed to keep oxygen and water from interacting with reactive precursor chemicals and freshly formed nanocrystals. Since this robot is controlled by software protocols, novice users can direct WANDA to perform complex workflows that traditionally require extensive chemistry experience.

Scientists have directed WANDA to produce and optimize a diverse set of nanomaterials under conditions analogous to those employed in traditional flask-based chemistry. Starting with widely studied and practically useful nanomaterials; such as cadmium selenide quantum dots, whose size can be adjusted to emit different colors of visible light. Scientists showed how WANDA can optimize the size, crystal structure and luminescence properties of different nanocrystals.

Scientists are expecting a revolutionary change in the way nanoscience research is performed. Not only does WANDA enable the optimization and mass production of nanoparticles users need, but this robot also facilitates experiments that give us a deeper understanding into the chemistry and physics of nanoscale materials.