Introduction
Overview
Nanotechnology is becoming a hot topic with investors. Many investors are coming to view it as the next major opportunities for long-term return, and pundits credit it with promising everything from curing all illness to revolutionizing computing. As with many hot labels, nanotechnology can be sized to fit the ambition of the entrepreneur and the appetite of the investor. This article briefly outlines the origins nanotechnology and then provides a framework of technology subfields, each with a different technology root.
The information in this article provides an appropriate background for the coming
Origin
Nanotechnology is the science, engineering, and manufacturing of sub-micrometer systems which perform designed-for tasks analogous or related to electrical, mechanical, biological, and computing systems. Biology provides a meaningful template for nanotechnology, as a plant or animal cell can be described as a collection of organelles - natural nanomachines - which collectively function to metabolize and sustain life.
The most widely quoted origin of nanotechnology as a concept is a lecture titled, "There's Plenty of Room at the Bottom", given at Caltech by Prof. Richard Feynman during a 1959 American Physical Society meeting. Therein, he proposed the extreme miniaturization of books, electrical motors, and computers, noted biological precedents for the very small, and talked about some of the challenges involved. The lecture was received with humor, as Feynman intended, and with skepticism.
The seeds Feynman planted took several decades to germinate, but they've grown like kudzu in the last decade. Nanometer-scale manipulation of individual atoms and molecules now occurs in many labs. Micron-scale devices for electronics and for mechanical actuators are commonplace, and the push to advance nanotechnology is in full force. Some examples:
- IBM researchers were awarded the Nobel prize in 1986 for the atomic force microscope, a variant of which is used to push atoms and molecules around surfaces.
- Chemists craft proteins which interact in a designed manner in part by selecting for the hydrophilic (water-loving) and hydrophobic (water-repellant) nature of different amino acids and then custom crafting the protein molecules. Self-assembly of molecules into designed structures has been researched actively for the last twenty years by several groups, some using DNA as a base molecule while others use molecular thin films. These are an integral component of molecular computing components being explored by a team from Rice, Penn, and Yale.
- The 1996 Chemistry Nobel was awarded for the first synthesis of the carbon and hydrogen "soccer ball" molecule, buckminsterfullerene, by Curl, Kroto, and Smalley. This started furious commercial development of fullerenes and led to the bulk manufacture of carbon nanotubes, which while produced by conventional chemistry are used in nanometric applications from atomic force microscopy to catalysis and in electronic interconnects. Carbon nanotubes are thin-walled large molecules constructed of closed carbon tubes - a modification graphite, the material used for common pencil "lead".
- Chemists have borrowed (from bacteria) stable photoactive molecules such as bacteriorhodopsin to investigate the construction of molecular-scale data storage among other applications. This is a heat-stable version of the light-sensing chemicals used for vision sensing in all animals.
There is a lot going on, and in a great many widely disparate disciplines. Precisely because the field began with so broad a definition, it has become a catchphrase for many fields of work. This breadth motivates the taxonomy introduced here.
Nanotechnology Taxonomy
Nanotechnology products include structures and materials with a highly organized and regular multi-dimensional nanometer-scale structure extending for many atomic or molecular distances. Examples include carbon nanotubes, DNA-based structures, and any system which manipulates or places atoms or molecules individually.
The discussion excludes materials which have randomly distributed nanometer scale features. For example, many conventional steels have a nano-scale grain structure. Some other excluded technologies include nanocrystalline powder manufacturing, thin-film vapor and plasma deposition manufacturing, and the lithographic processing of features larger than 0.1 micron, the limit of today's ultraviolet lithography methods. In addition, much of the work in micromechanical silicon devices is larger than the nanometer scale.
The taxonomy below divides by manufactured state, chemistry of fabrication, and means of arrangement. These three criteria provide the background for examining the applied use of nanotechnology and the market opportunites they represent.
Manufactured State
Manufactured state refers to whether the item created is meant essentially a finished product or to be used to create a product.
Device is the term used to represent a completely functional machine or the finished subcomponent of another device. Generally speaking, devices require little to no additional work to be used.
Material, on the other hand, refers to an unfinished product used to construct a device. Materials often require additional sorting, fabrication or bulk processing before they are used productively.
Fabrication Chemistry
Fabrication chemistry refers to the chemical reactions used to build the device or material.
Organic chemistry uses elements common to biology, principally carbon, hydrogen, oxygen, and nitrogen, typically involving them in aqueous reactions. Biochemists and organic chemists have discovered and learned from biology, gaining a rich set of tools for manipulation on the molecular scale; many of the reactions used are found in nature. All organic construction occurs within the temperature range of liquid water.
Inorganic chemistry involves either primarily inorganic compounds or non-aqueous chemistry. For example, the synthesis of carbon nanotubes is a non-aqueous process, involving the blasting of a carbon rod with a pulsed laser.
Assembly
Assembly refers to how a material or device is physically put together or comes into being.
Self-assembly refers the ability for a set of molecules or small structures to arrange themselves into an ordered and desired state through a combination of random motion and mutual attraction; essentially the molecules seek a lower energy state. Self-assembly may rely on a highly specific catalytic surface to facilitate assembly. An example of a self-assembling structure are the lipo-protein walls of a bacterial cell.
Constructed arrangement is the act of physically creating a material or device. This may be performed by the needle of an atomic force microscope or by the action of a lithographic process.
Uses of the Taxonomy
Manufactured Inorganic Materials
This subclass of nanoscale structure materials includes the fullerene structures, such as carbon nanotubes, as well as the new superlattice thermoelectric materials (which convert temperature differences into electricity) discovered by the Research Triangle Institute. Both are examples of essentially non-organic materials produced (or will be produced) in a bulk process and used as part of a device. Applications of fullerene structures include energy storage, cathodes for flat panel displays, drug delivery, and chemical catalysis.
Self-Assembling Organic Materials
This subclass of nanoscale material is characterized by the usage of organic, typically aqueous, methods in producing the materials. Outside nanotechnology, plastics are one of the most famous class of materials resulting from organic chemistry. Within nanotech, organic engineered materials include biopolymers produced using monolayer methods. Naturally occurring biopolymers include collagen, a building block of skin and cartilage. These have potential applications ranging from computation and data storage to medicine.
Self-Assembling Inorganic Materials
This fairly forwarding looking process takes biology as something of a template for understanding how to build ordered materials from component building blocks. Some intriguing ceramic materials have been constructed this way. In addition, Sandia Labs has shown that carefully selected inks evaporate into nanoscale structures.
Self-Assembling Organic Devices
The engineering of these devices takes advantage of the rich chemistry found within nature. Every bacterial cell contains a broad array of complex organelles, each essentially acting as a "wet" molecular device performing a specific cellular function such as energy production or protein synthesis.
While purpose-built molecular devices have been postulated for some time, the basic science in this area has proceeded well for the last two decades. For example, scientist now have a detailed understanding of the structure and function of the rotating "tails", flagella, which propel many kinds of cells, such as spermatozoa, through water. Even with these advances the long sought injectable artery-cleaners are still fiction; if new therapeutic molecular devices can be produced, a medical renaissance could result.
Commercializatin of self-assembling organic devices has begun however. For example, a team form Rice, Yale, and University of Pennsylvania have formed a company called Molecular Electronics. They are looking to commercialize the molecular self-assembly of logic elements onto a silicon substrate.
Self-Assembling Inorganic Devices
Inorganic self-assembly of devices is currently extremely forward looking. Much of this research is in the formative stages, typically occurring in universities. For example, DARPA sponsors a program at the University of Pennsylvania directed at taking membrane assembly methods of biology and applying them to metal and semiconductor objects. This area could result in extremely powerful new technologies, but has to essentially invent a new chemistry to come of age.
Constructed Inorganic Devices
Most applications of nanotechnology using inorganic materials involve constructed devices. These include both true nanoscale devices and devices which employ nanoscale materials. These range from quantum-scale electronics formed using e-beam lithography, to display devices constructed using carbon nanotubes as cathodes.
The electronics industry is moving quickly to understand and exploit the physics involved in this regime in order to continue producing gains in computing power, without commensurate gains in power consumption, as quantum limits are approached. For example:
- Intel, IBM, and many other major chip producers participate or sponsor efforts aimed at understanding quantum effects and single-electron device physics.
- HP Labs has an active group studying quantum electronics.
- Samsung and ISE are some of the major competitors in display manufacturing investigating the use of carbon nanotube materials.
- IBM has recently announced a molecular scale memory technology with data densities of about one terabyte (1000 GB) per square inch.
Conclusion
The word nanotechnology describes a broad set of technologies that provide novel materials, processes, and devices from companies and researchers that are attempting to break today's fundamental technological limits.
Part Two of this article outlines technologies, and their possible opportunities, that span the outlined taxonomy, describing the technologies within the context of several markets.
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