"Nanotool" is a term used to describe a range of devices, molecules and systems which function at the nanometer scale. Still in the early stages of development, these devices will have extraordinary medical, manufacturing, electronic, chemical and many other applications. 

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Example Nanotools include:

	Nanomotors
	Nanogears
	Nanopumps
	Nanotubes
	Nanoprisms
	AFM Dip Pens
	Nanowire
	Nanopowders
	Nanospheres
	Nanodots
	Nanochips

Nanomotors

Small, molecular-scale motors have enormous potential over a broad range of sectors.  Functional nanomotor devices could be used medically to remove lipid / fat deposits from arteries, as sensors for biodiagnostics or for microfabrication and assembly of other nanodevices. A number of research groups have fabricated molecular motors from DNA - some from a single molecule of DNA!

Structurally these motors have unique shapes and functions:

	"Inchworm" - stretch and retract capability
	"Assemblers" - attach selected molecules to other molecules
	"Tweezers" - pick-up and manipulate molecules
	"Illuminators" - add light emitting / quenching components
	"Transporters" - selectively move materials

Individually these simple molecular-level functions may not appear significant, but in combinations they have remarkable potential. Fabrication of molecules, attachment of anticancer drugs directly to tumor cells, diagnosis of aberrant DNA sequences and disease conditions (clinical therapies), bioseparation of any number of molecules, assembly of micro-electronics and many other applications.

Nanowire

Nanowires are materials capable of conducting the flow of electrical current and are physically in the nanoscale range (10^-9m). Nanowires have been assembled from a range of materials:

	Conductors include Gold, Platinum, Nickel
	Insulators include Silica Oxides and other substances
	Semi-conductors made from Silca and other materials

Interestingly, the properties of electron flow through nanowires are considered to be "quantum limited" since the nanowires are so narrow (laterally) that in some cases only a single electron at one time can pass through.

Nanowires to not occur naturally and are artificially manufactured from the materials described above, by assembly of individual atoms or through etching away material from a larger (but still microscopic) structure.

In terms of electronic properties, nanowires are far more sensitive to "edge effects" as compared to large-scale traditional wires - the outside component molecules of the nanowire affecting electron travel.  Another complication is quantiziation whereby electrons in nanowires can only possess specific levels of energy (rather than input = output in full scale systems).

Directed growth of nanowires - self assembly of circuits

One interesting aspect of nanowire technology is the current development of systems which allow the nanowires to "grow" in predictable ways. Although still in early development, the potential for self-assembly of circuits is obviously significant. Applications include nano-wiring and wiring replacement, linkages between other nano components and circuitry, the creation of logic circuits and semi-transistors.

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Nanowires can also play a role in computing by using nanowires as channels to create Field-Effect Transistors (FET) which allow a significant reduction in moderm computer silicon-based CMOS technology.

Dip Pens - Dip Pen Nanolithography

Construction of many nanodevices is based in "dip pen nanolithography" (DPN) created by Naolnk Inc. The idea is to build structures by accurately positioning molecules on a surface using a liquid-solid meniscus interface. DPN is a technology that will be used to fabricate many different nano-devices. In many respects DPN operates much like a pen writing on paper - the fundamental difference being that a layer of molecules is being positioned (with molecular accuracy) on an appropriate substrate / surface. 

http://www.chem.northwestern.edu/~mkngrp/dpn.htm

Creation of precise molecular entities is also referred to as "nano-patterning."  In some ways DPN patterning operates like a programmable inkjet printer, applying molecules to meet exacting specifications. This is a one-step process, as compared to photolithographic techniques with creation of successive layers and subsequent etching to produce molecular structures. The "nozzle" of the "pen" is the tip of an Atomic Force Microscope (AFM) cantilever which allows precise application of molecules.

Applications of Dip Pen Nanolithography

There many, many potential applications for DPN, including:

	fabrication of silicon nanostructures
	ultra high-density nano-arrays
	creation of conductive polymers
	assembly of organic molecules

Thermally-Controlled DPN

A new development in Dip Pen Nanolithography is the use of temperature to stop / start the flow of molecules from the AFM cantilever. This provides a more complete control of the deposition process. The mechanism is simple: cold means no ink or molecule deposition, while heat causes an immediate flow onto the substrate.

NanoPowders

Nanopowders are particles typically below 50 nm in diameter. Behaviourly, nanoparticles are able to move relatively freely past each other and resemble more of a fluid or "smoke" than a solid material. Nanoparticles are a fundamental building block of many other nano-materials.

There are two main types of nanopowders:

	Simple Nanopowders - single cation present
	Complex Nanopowders - multiple cations in formula

Applications of Nanopowders

There are numerous applications for nanopowders. Examples include:

	Inks, conductive coatings and films for deposition
	Microelectronic circuit construction
	Biodiagnostics and medical devices, bioelectronics
	Fuel Cells, batteries and storage devices

NanoTubes

The nanotube can serve many purposes: to create the foundation of more complex molecular  structures, to fabricate nanogears and motors, to act as nanowires to channel electron flow, or simply as microscopic tubes to passively sort biomolecules (see also Nanomedicine).

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 Nanotubes are typically fabricated out of rolled sheets of hydrocarbons but other materials may be employed as well. Recently, the use of AFM (atomic force microscopy) cantilever techniques have allowed scientists to manipulate, position, cut, add or alter nanotube structures at their discretion, making a significant addition to the other nano-tools currently available. An interesting observation is that nanotubes are strobgly influenced by the inter-molecular Van der Waals forces emanating from the surface they are placed on - the nanotube structure and shape can be influenced by it's environment.  The indication is that alterations in shape may also be employed to change the functional properties of the nanotubes themselves. 

Categories of nanotubes include:

	SWNT - single-walled nanotubes (one layer)
	MWNT - multi-walled nanotubes (multiple layers)
	Fullerites - polymerized multi-walled nanotubes
	Torus - nanotube compressed into a "donut" shape

Physically nanotubes have two important characteristics:

	Strength - remarkable physical strength
	Flexibility - amazing elasticity and flexibility

Initial work has indicated that optical properties of nanoprisms can be altered by:

	Chemical composition
	Physical size
	Shape and morphology

This holds potential for usage as optical detectors for a variety of purposes, including:

	molecular-scale electronics
	biosensors and biodiagnostics
	chemical testing and measurement
	quantification and qualitative assessments
	electro-mechanical interfaces and signaling
	communications / signaling

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Nanoprisms are produced using light energy to  convert silver nanospheres into molecular prisms and are used in combinations  of individual nanosphere molecules.

NanoSpheres

Nanospheres are sub-microscopic spheres which not only have applications themselves as vehicles todeliver controlled-release therapies and drug delivery, but also as raw materials for assembly of numerous other nanoscale materials.

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Useful characteristics of nanospheres include:

1. Size - small enough for cellular introduction - a useful characteristic in controlled drug delivery.
2. Pores - small pores allow for controlled release of molecules. Nanosphere shape controls the selectivity of molecule capture.
3. Adsorbent - can adsorb small molecules and ions. If allowed to adsorb Iron, nanospheres can then interact with magnetic fields for signaling and physical manipulation.
4. Inert - depending on the chemical composition, nanospheres can be employed as highly useful coatings on nanochips and electronic circuits.

Nanospheres have been constructed of silica or carbon molecules and typically range from 2 to 50 nm.  A number of companies custom manufacture nanospheres for a range of nanotechnology industries.

NanoDots

Nanodots are a simple nanotool that may prove to have exceptional significance.  The ability to create nano-scale dots on micro and nano-circuits has obvious electronic applications, but there is much more to nanodot technology than existing as a simple component of more complex electronic devices. Nanodots have fabricated in a number of ways, including the use of STM (scanning tunneling microscopy) to apply molecules to a substrate.

Applications of Nanotdots are diverse and include:

	Plastics, polymers and coatings
	Superconducting wires and circuits
	Insulators from magnetic and thermal interference
	Customization of optical and electromagnetic properties
	Computer memory

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One group of researchers has been using nickel nanodots comprised of several hundred individual molecules. What is exceptional, however, is that these nickel nanodots have two distinct magnetic states: "on and off".  Simple, but also the core requirement for binary coding for modern computer systems. A nanodot-based computer chip could hold terabytes of information in a centimeter-wider chip.  The enormous increase in storage capacity is the result of the ability to place nanodots exceptionally close to each other (as opposed to a contemporary hard drive).

Human breast cancer cells tagged with quantum dots.

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Other potential applications for nanodots includes the fabrication of Single Electron Transistors (SET) to create incredibly microscopic light-emitting devices with numerous applications.