Presentation1finallll Nanotech

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KIRTI BIHANI TEJAS BODAS ASHISH CHATURVEDI SHASHWAT HEGDE RAJESH IYER

• The observation made in 1965 by Gordon Moore, co-founder of Intel, that the number of transistors per square inch on integrated circuits had doubled every year since the integrated circuit was invented. Moore predicted that this trend would continue for the foreseeable future. In subsequent years, the pace slowed down a bit, but data density has doubled approximately every 18 months, and this is the current definition of Moore's Law, which Moore himself has blessed. Most experts, including Moore himself, expect Moore's Law to hold for at least another two decades.

Nanotechnology is an umbrella term that covers many areas of research dealing with objects that are measured in NANOMETERS. A NANOMETER (nm) is a billionth of a meter, or a millionth of a millimeter. The goal of nanotechnology is to manipulate atoms individually and place them in a pattern to produce a desired structure.

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Of the various lithography methods, dip-pen lithography using AFM setup is receiving considerable attention in the recent years. In our laboratory, well characterized metal sols and other colloidal dispersions have been used as inks for dip-pen raised patterns. Using this method, nanoscale rectangles filled with the metal nanocrystals have been drawn on mica substrates at different aspect ratios, the narrowest line being 20 nm wide. Besides metal sols, dispersions with interesting fluorescing properties such as Eu doped LaPO4 nanoparticles have been tried out as inks. Colloidal gamma-Fe2O3 has also been used to produce magnetic patterns. In some instances, silicon substrates have been used. The internal structure of the patterns has been studied using XPEEM and LEEM techniques on a synchrotron beamline. The method is being used for patterned synthesis for nanoobjects on surfaces as well as for making nanocircuitry.

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Dip-Pen Nanolithography (DPN) is a scanning probe nanopatterning technique in which an AFM tip is used to deliver molecules to a surface via a solvent meniscus, which naturally forms in the ambient atmosphere. This direct-write technique offers high-resolution patterning capabilities for a number of molecular and biomolecular 'inks' on a variety of substrates, such as metals, semiconductors, and monolayer functionalized surfaces. It's becoming a work-horse tool for the scientist interested in fabricating and studying soft- and hard-matter on the sub-100nm length scale. DPN allows one to precisely pattern multiple patterns with near-perfect registration. It's both a fabrication and imaging tool, as the patterned areas can be imaged with clean or ink-coated tips. The ability to achieve precise alignment of multiple patterns is an additional advantage earned by using an AFM tip to write, as well as read nanoscopic features on a surface. These attributes make DPN a valuable tool for studying fundamental issues in colloid chemistry, surface science, and nanotechnology. For instance, diffusion and capillarity on a surface at the nanometer level, organization and crystallization of particles onto chemical or biomolecular templates, monolayer etching resists for semiconductors, and nanometer-sized tethered polymer structures can be investigated using this technique.

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How does DPN work? In order to create stable nanostructures, it's beneficial to use molecules that can anchor themselves to the substrate via chemisorption or electrostatic interactions. When alkanethiols are patterned on a gold substrate, a monolayer is formed in which the thiol headgroups form relatively strong bonds to the gold and the alkane chains extend roughly perpendicular to surface.

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What are the attributes of DPN? Creating nanostructures using DPN is a single step process which does not require the use of resists. Using a conventional atomic force microscope (AFM) it is possible to achieve ultrahigh resolution features with linewidths as small as 10-15 nm with ~ 5 nm spatial resolution. For nanotechnological applications, it is not only important to pattern molecules in high resolution, but also to functionalize surfaces with patterns of two or more components.

A) Ultra-high resolution pattern of mercaptohexadecanoic acid on atomically-flat gold surface. B) DPN generated multicomponent nanostructure with two aligned alkanethiol patterns. C) Richard Feynmann's historic speech written using the DPN nanoplotter. One of the most important attributes of DPN is that, because the same device is used to image and write a pattern, patterns of multiple molecular inks can be formed or aligned on the same substrate. With the aid of software created inhouse (which has been commercialized through NanoInk), we have devised a nanolithographic tool which is ink-general and allows for simple registration of inks. Also, the contamination which could result from typical lithographic techniques (such as photolithography), is avoided.

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What are the applications of DPN? We are currently using DPN to probe fundamental surface science questions as well as to create technologically relevant nanostructures. Some of the applications that we are targeting are depicted in the figure below. Part of the process of investigating these technological applications requires that we develop methods which will allow parallel patterning in addition to the serial capabilities of DPN. In addition, we have to develop procedures to pattern on semiconductor and insulator substrates as well as metals, and also extend the choice of inks past small molecules to biological polymers and conducting organic macromolecules.

Definition: Carbon Nanotubes • Single-wall carbon nanotubes are a new form of carbon made by rolling up a single graphite sheet to a narrow but long tube closed at both sides by fullerenelike end caps.. • However, their attraction lies not only in the beauty of their molecular structures: through intentional alteration of their physical and chemical properties fullerenes exhibit an extremely wide range of interesting and potentially useful properties.

Properties (2) • The chart compares the tensile strength of SWNT's to some common high-strength materials. • Nanotubes can be either electrically conductive or semiconductive, depending on their helicity. • These one-dimensional fibers exhibit electrical conductivity as high as copper, thermal conductivity as high as diamond, • Strength 100 times greater than steel at one sixth the weight, and high strain to failure. • Current length limits are about one millimeter.

Current Applications • Carbon Nano-tubes are extending our ability to fabricate devices such as: • Molecular probes • Pipes • Wires • Bearings • Springs • Gears • Pumps

Manufacturing Techniques

• Evaporation of solid carbon in arc discharge, • Laser ablation, • Catalytic chemical vapor deposition of carbon containing gases • Catalytic decomposition of fullerenes

Future Applications

• Molecular transistors. • Field emitters. • Building blocks for bottom-up electronics. • Smaller, lighter weight components for next generation spacecraft. • Enable large quantities of hydrogen to be stored in small low pressure tanks. • Space elevator, Instead of blasting off for the heavens astronauts could reach the ISS as easily as they would a department store: “Next floor, LEO, watch your step please!”

• These nanorobots will need to be powered by the reactions of atoms, or the spin of electrons, rather than the conventional electric motor and battery. • Nanorobots could possibly use biochemical motors spinning nanogears to power flagella-like tails.

GEARS CREATED OUT OF NANOTUBES COURTESY OF NASA.GOV

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In order to create these nanocomponents, scientists must be able to manipulate atoms into desired positions. In 1990, using an atomic force microscopy instrument, researchers positioned individual atoms into a familiar logo.

For nanorobots, a system must be created that could automatically place atoms into the desired position, if millions are to be made.

Applications of Nanorobots • Nanorobots could be used in medicine to treat illnesses • They could quickly manufacture other nanodevices, such as electronics • Or create “smart” electronic circuits that could repair themselves.

Applications in Medicine • Nanorobotics has the potential to revolutionize medicine. • If nanodevices were created that could be released into the body, target cancerous cells or viruses, then destroy these threats, many diseases could be cured.

• Nanorobots provide precision. • Because these nanorobots would target only diseased cells, they would be a great improvement over current methods of treating cancer.

• For the detection of cancerous cells, these robots could use cantilevers. • Cantilevers, tiny levers, can be engineered to bind to cancerous cells, causing them to bend when cancer is present.

Dendrimers •Dendrimers are man-made molecules with a high surface area that can bind to drugs. •With a molecule to recognize cancerous cells attached, these dendrimers could become an advanced drug delivery system.

Control • Nanorobots require some type of guidance and control to perform their tasks. • Nanorobots could either be remotely controlled by a computer or autonomous. • Autonomous robots would require a nanocomputer, which may seem like a ridiculous idea, but with the miniaturization of circuits this may be possible in the future.

In the near future, this nanorobot of science fiction may become a reality.