BIO-INSPIRED NANOTECH?

Biologically inspired nanotechnology

Nanoscience is the design and fabrication of materials from the nanometer-length scale up to create novel and significantly improved devices and materials. In contrast, traditional materials science builds from large-scale objects down. The semiconductor industry, for example, has relied on developing smaller and smaller features in large silicon wafers to fabricate computer chips. In contrast, using a nanoscience approach, one can self-assemble chains of molecules to replace wires on conventional computer chips, and it allows the semiconductor industry to produce revolutionary computer chips that are not only smaller, but also faster and more powerful than anything that exists today.
To put a nanometer-length scale into perspective, one nanometer—one billionth of a meter—is 100,000 times smaller than the width of a human hair. The building blocks in the biological world are nanometer-sized molecules such as proteins and sugars that, when assembled into intermediate length-scaled objects, deter- mine and control biological function.

In addition to developing nanoelectronics, many other features of the biosynthetic process lend themselves to devising nanotechnological materials. To do its work, nature uses highly sophisticated processes, for example, selection; self-organization; and self- assembly to provide an enormous range of "bio"-materials that ultimately form cells, tissues and organs. These materials exhibit remarkable powers of memory, replication, self-healing and self-repair.

In the case of bone, for example, nature has developed a composite ceramic material with overlap- ping levels of structural hierarchy and functional complexity. Self-assembled bio-organic materials, such as lipids and proteins, form nanoscale templates for inorganic components, guiding the final structure and shape of bone. It is the mixture of two very different materials—inorganic silicates and organic proteins— that gives bone its exceptional strength.

Biological membranes, which encapsulate all cellular machinery, represent another such example. Here, nanoscale organization and complex interactions of its constituents such as lipids and cholesterol, allow them to filter undesirable molecules from entering the cell. Recent advances in materials synthesis and biotechnology have enabled scientists to use these lessons from biology to produce highly ordered nanostructured materials with unique properties.

At Los Alamos National Laboratory, researchers recently have developed nanofilters by mimicking the biosynthesis of bone. These nanofilters are made up of ordinary glass, which has pores and channels that can be adjusted in size from four to 20 nanometers. By controlling the size and chemical properties of the pores, the constituents of complex mixtures can be separated. These nanofilters could be employed, for example, as masks to prevent exposure to biological pathogens such as viruses that can be as small as 30 nanometers in diameter. This work is supported by the Department of Energy's Office of Basic Energy Sciences in a joint project with Sandia National Laboratories and the University of New Mexico.

Los Alamos researchers also have developed miniaturized biosensors that can detect bioagents and markers for disease by mimicking cellular membranes and depositing these membranes onto optical chips. The surface of these membrane-based sensors look like the natural target of a biological agent, receptor molecules that decorate the surface of a cell membrane. By copying nature's functions using nanoscaled materials, the useful properties of sensors can be optimized permitting entirely new approaches to, for example, the early detection of disease. This cross-disciplinary effort spans fundamental science in Los Alamos' Strategic and Supporting Research Directorate and systems engineering in the Threat Reduction Directorate and is supported by the departments of Energy and Defense and by Laboratory-Directed Research and Development funds (see "Early Detection for Protection" for more on LDRD projects))

CARBON NANOTUBES?

Carbon nanotubes (CNTs; also known as buckytubes) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,which is significantly larger than any other material. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors.
Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The ends of a nanotube might be capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to 18 centimeters in length (as of 2010). Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).
The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forces.

Extreme carbon nanotubes
Cycloparaphenylene
The observation of the longest carbon nanotubes (18.5 cm long) was reported in 2009. They were grown on Si substrates using an improved chemical vapor deposition (CVD) method and represent electrically uniform arrays of single-walled carbon nanotubes.
The shortest carbon nanotube is the organic compound cycloparaphenylene which was synthesized in the early 2009.
The thinnest carbon nanotube is armchair (2,2) CNT with a diameter of 3 Å. This nanotube was grown inside a multi-walled carbon nanotube. Assigning of carbon nanotube type was done by combination of high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and density functional theory (DFT) calculations.
The thinnest freestanding single-walled carbon nanotube is about 4.3 Å in diameter. Researchers suggested that it can be either (5,1) or (4,2) SWCNT, but exact type of carbon nanotube remains questionable. (3,3), (4,3) and (5,1) carbon nanotubes (all about 4 Å in diameter) were unambiguously identified using more precise aberration-corrected high-resolution transmission electron microscopy. However, they were found inside of double-walled carbon nanotubes.

NANO ROBOTICS?

Nanorobotics is the technology of creating machines or robots at or close to the microscopic scale of a nanometer (10−9 meters). More specifically, nanorobotics refers to the still largely hypothetical nanotechnology engineering discipline of designing and building nanorobots, devices ranging in size from 0.1-10 micrometers and constructed of nanoscale or molecular components. As no artificial non-biological nanorobots have yet been created, they remain a hypothetical concept. The names nanobots, nanoids, nanites or nanomites have also been used to describe these hypothetical devices.
Another definition is a robot that allows precision interactions with nanoscale objects, or can manipulate with nanoscale resolution. Following this definition even a large apparatus such as an atomic force microscope can be considered a nanorobotic instrument when configured to perform nanomanipulation. Also, macroscale robots or microrobots that can move with nanoscale precision can also be considered nanorobots.
Nanomachines are largely in the research-and-development phase, but some primitive molecular machines have been tested. An example is a sensor having a switch approximately 1.5 nanometers across, capable of counting specific molecules in a chemical sample. The first useful applications of nanomachines, if such are ever built, might be in medical technology, where they might be used to identify cancer cells and destroy them. Another potential application is the detection of toxic chemicals, and the measurement of their concentrations, in the environment. Recently, Rice University has demonstrated a single-molecule car developed by a chemical process and includes buckyballs for wheels. It is actuated by controlling the environmental temperature and by positioning a scanning tunneling microscope tip.




Nanorobotics theory
Since nanorobots would be microscopic in size, it would probably be necessary for very large numbers of them to work together to perform microscopic and macroscopic tasks. These nanorobot swarms, both those incapable of replication (as in utility fog) and those capable of unconstrained replication in the natural environment (as in grey goo and its less common variants), are found in many science fiction stories, such as the Borg nanoprobes in Star Trek. The word "nanobot" (also "nanite", "nanogene", or "nanoant") is often used to indicate this fictional context and is an informal or even pejorative term to refer to the engineering concept of nanorobots. The word nanorobot is the correct technical term in the nonfictional context of serious engineering studies.
Some proponents of nanorobotics, in reaction to the grey goo scare scenarios that they earlier helped to propagate, hold the view that nanorobots capable of replication outside of a restricted factory environment do not form a necessary part of a purported productive nanotechnology, and that the process of self-replication, if it were ever to be developed, could be made inherently safe. They further assert that free-foraging replicators are in fact absent from their current plans for developing and using molecular manufacturing
Potential applications

Nanomedicine
Potential applications for nanorobotics in medicine include early diagnosis and targeted drug delivery for cancer, biomedical instrumentation, surgery, pharmacokinetics, monitoring of diabetes, and health care.
In such plans, future medical nanotechnology is expected to employ nanorobots injected into the patient to perform treatment on a cellular level. Such nanorobots intended for use in medicine should be non-replicating, as replication would needlessly increase device complexity, reduce reliability, and interfere with the medical mission. Instead, medical nanorobots are posited to be manufactured in hypothetical, carefully controlled nanofactories in which nanoscale machines would be solidly integrated into a supposed desktop-scale machine that would build macroscopic products.
The most detailed theoretical discussion of nanorobotics, including specific design issues such as sensing, power communication, navigation, manipulation, locomotion, and onboard computation, has been presented in the medical context of nanomedicine by Robert Freitas. Some of these discussions remain at the level of unbuildable generality and do not approach the level of detailed engineering.

Nanorobots

Nanotechnology promises futuristic applications such as microscopic robots that assemble other machines or travel inside the body to deliver drugs or do microsurgery.These machines will face some unique physics. At small scales, fluids appear as viscous as molasses, and Brownian motion makes everything incessantly shake. Taking inspiration from the biological motors of living cells, chemists are learning how to utilize protein dynamics to power microsize and nanosize machines with catalytic reactions.

QUANTUM DOTS

A quantum dot is a semiconductor whose excitons are confined in all three spatial dimensions. As a result, they have properties that are between those of bulk semiconductors and those of discrete molecules. They were discovered by Louis E. Brus, who was then at Bell Labs. The term "Quantum Dot" was coined by Mark Reed. Researchers have studied quantum dots in transistors, solar cells, LEDs, and diode lasers. They have also investigated quantum dots as agents for medical imaging and hope to use them as qubits.
In layman's terms, quantum dots are semiconductors whose conducting characteristics are closely related to the size and shape of the individual crystal. Generally, the smaller the size of the crystal, the larger the band gap, the greater the difference in energy between the highest valence band and the lowest conduction band becomes, therefore more energy is needed to excite the dot, and concurrently, more energy is released when the crystal returns to its resting state. For example, in fluorescent dye applications, this equates to higher frequencies of light emitted after excitation of the dot as the crystal size grows smaller, resulting in a color shift from red to blue in the light emitted. The main advantages in using quantum dots is that because of the high level of control possible over the size of the crystals produced, it is possible to have very precise control over the conductive properties of the material.

Quantum dots are particularly significant for optical applications due to their high extinction co-efficient [13]. In electronic applications they have been proven to operate like a single-electron transistor and show the Coulomb blockade effect. Quantum dots have also been suggested as implementations of qubits for quantum information processing.
The ability to tune the size of quantum dots is advantageous for many applications. For instance, larger quantum dots have a greater spectrum-shift towards red compared to smaller dots, and exhibit less pronounced quantum properties. Conversely, the smaller particles allow one to take advantage of more subtle quantum effects.

Application

Researchers at Los Alamos National Laboratory have developed a wireless device that efficiently produces visible light, through energy transfer from thin layers of quantum wells to crystals above the layers.
Being zero dimensional, quantum dots have a sharper density of states than higher-dimensional structures. As a result, they have superior transport and optical properties, and are being researched for use in diode lasers, amplifiers, and biological sensors. Quantum dots may be excited within the locally enhanced electromagnetic field produced by the gold nanoparticles, which can then be observed from the surface Plasmon resonance in the photoluminescent excitation spectrum of (CdSe)ZnS nanocrystals. High-quality quantum dots are well suited for optical encoding and multiplexing applications due to their broad excitation profiles and narrow/symmetric emission spectra. The new generations of quantum dots have far-reaching potential for the study of intracellular processes at the single-molecule level, high-resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics.

NANOTECHNOLOGY?

Nanotechnology shortened to "nanotech", is the study of the controlling of matter on an atomic and molecular scale. Generally nanotechnology deals with structures of the size 100 nanometers or smaller in at least one dimension, and involves developing materials or devices within that size. Nanotechnology is very diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the nanoscale to investigating whether we can directly control matter on the atomic scale.
There has been much debate on the future implications of nanotechnology. Nanotechnology has the potential to create many new materials and devices with a vast range of applications, such as in medicine, electronics and energy production. On the other hand, nanotechnology raises many of the same issues as with any introduction of new technology, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as speculation about various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.

Current Research

1  Nanomaterials

2  Bottom-up approaches
3  Top-down approaches
4  Functional approaches


1  Nanomaterials
This includes subfields which develop or study materials having unique properties arising from their nanoscale dimensions. Interface and colloid science has given rise to many materials which may be useful in nanotechnology, such as carbon nanotubes and other fullerenes, and various nanoparticles and nanorods. Nanomaterials with fast ion transport are related also to nanoionics and nanoelectronics.
Nanoscale materials can also be used for bulk applications; most present commercial applications of nanotechnology are of this flavor.
                                        Progress has been made in using these materials for medical applications; see Nanomedicine. Nanoscale materials are sometimes used in solar cells which combats the cost of traditional Silicon solar cells. Development of applications incorporating semiconductor nanoparticles to be used in the next generation of products, such as display technology, lighting, solar cells and biological imaging; see quantum dots.

2 Bottom-up approaches
These seek to arrange smaller components into more complex assemblies.
DNA nanotechnology utilizes the specificity of Watson–Crick basepairing to construct well-defined structures out of DNA and other nucleic acids.
Approaches from the field of "classical" chemical synthesis also aim at designing molecules with well-defined shape(e.g. bis peptide) . More generally, molecular self-assembly seeks to use concepts of supramolecular chemistry, and molecular recognition in particular, to cause single-molecule components to automatically arrange themselves into some useful conformation.

3 Top-down approaches
These seek to create smaller devices by using larger ones to direct their assembly.
Many technologies that descended from conventional solid-state silicon methods for fabricating microprocessors are now capable of creating features smaller than 100 nm, falling under the definition of nanotechnology. Giant magnetoresistance-based hard drives already on the market fit this description, as do atomic layer deposition (ALD) techniques. Peter Grünberg and Albert Fert received the Nobel Prize in Physics for their discovery of Giant magnetoresistance and contributions to the field of spintronics in 2007.
Solid-state techniques can also be used to create devices known as nanoelectromechanical systems or NEMS, which are related to microelectromechanical systems or MEMS.
Atomic force microscope tips can be used as a nanoscale "write head" to deposit a chemical upon a surface in a desired pattern in a process called dip pen nanolithography. This fits into the larger subfield of nanolithography.
Focused ion beams can directly remove material, or even deposit material when suitable pre-cursor gasses are applied at the same time. For example, this technique is used routinely to create sub-100 nm sections of material for analysis in Transmission electron microscopy.

4  Functional approaches
These seek to develop components of a desired functionality without regard to how they might be assembled.
Molecular electronics seeks to develop molecules with useful electronic properties. These could then be used as single-molecule components in a nanoelectronic device. For an example see rotaxane.
Synthetic chemical methods can also be used to create synthetic molecular motors, such as in a so-called nanocar.