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NANO SENSORS

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Nanosensors are any biological, chemical, orsugery sensory points used to conveyinformation about nanoparticles to the

macroscopic world . Their use mainly include various medicinal

purposes and as gateways to building othernanoproducts, such as computer chips thatwork at the nanoscale and nanorobots.

Presently, there are several ways proposed tomake nanosensors, including

Top-down and bottom-up design

bottom-up assembly

molecular self-assembly

top down lithography

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Currently, the most common mass-produced functioning nanosensors exist in the biologicalworld as natural receptors of outside stimulation.

For instance, sense of smell, especially in animals in which it is particularly strong, such asdogs, functions using receptors that sense nanosized molecules

Certain plants, too, use nanosensors to detect sunlight; various fish use nanosensors to detectminuscule vibrations in the surrounding water

One of the first working examples of a synthetic nanosensor was built by researchers at theGeorgia Institute of Technology in 1999

. It involved attaching a single particle onto the end of a carbon nanotube and measuring thevibrational frequency of the nanotube both with and without the particle

. The discrepancy between the two frequencies allowed the researchers to measure the massof the attached particle

Chemical sensors, too, have been built using nanotubes to detect various properties of gaseousmolecules.

Carbon nanotubes have been used to sense ionization of gaseous molecules while nanotubesmade out of titanium have been employed to detect atmospheric concentrations of hydrogen atthe molecular level. Many of these involve a system by which nanosensors are built to have aspecific pocket for another molecule.

When that particular molecule, and only that specific molecule, fits into the nanosensor, andlight is shone upon the nanosensor, it will reflect different wavelengths of light and, thus, be a

different color

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There are currently several hypothesized ways to produce nanosensors.

Top-down lithography

It is the manner in which most integrated circuits are now made.

It involves starting out with a larger block of some material and carving outthe desired form. These carved out devices, notably put to use in specificmicroelectromechanical systems used as microsensors, generally onlyreach the micro size, but the most recent of these have begun to incorporatenanosized components

bottom-up method, which involves assembling the sensors out of even more minuscule

components, most likely individual atoms or molecules.

This would involve moving atoms of a particular substance one by one intoparticular positions which, though it has been achieved in laboratory testsusing tools such as atomic force microscopes, is still a significant difficulty,

especially to do en masse, both for logistic reasons as well as economicones.

Most likely, this process would be used mainly for building starter moleculesfor self-assembling sensors.

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self-assembly, It is the The third way, which promises far faster results, involves

It is also said as growing particular nanostructures to be used as sensors.

This most often entails one of two types of assembly.

The first involves using a piece of some previously created or naturally formednanostructure and immersing it in free atoms of its own kind . After a givenperiod, the structure, having an irregular surface that would make it prone to

attracting more molecules as a continuation of its current pattern, would capturesome of the free atoms and continue to form more of itself to make largercomponents of nanosensors.

The second type of self-assembly starts with an already complete set of componentsthat would automatically assemble themselves into a finished product.

Though this has been so far successful only in assembling computer chips at themicro size, researchers hope to eventually be able to do it at the nanometer size formultiple products, including nanosensors.

Accurately being able to reproduce this effect for a desired sensor in a laboratorywould imply that scientists could manufacture nanosensors much more quickly and

potentially far more cheaply by letting numerous molecules assemble themselveswith little or no outside influence, rather than having to manually assemble each