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Nanobiomaterials in Clinical Dentistry
By Karthikeyan Subramani, Waqar Ahmed, James K. Hartsfield Jr. Elsevier
Copyright © 2013 Elsevier Inc.
All rights reserved.
ISBN: 978-1-4557-3129-9
CHAPTER 1
Introduction to Nanotechnology
Waqar Ahmed, Abdelbary Elhissi and Karthikeyan Subramani
CHAPTER OUTLINE
1.1 Introduction 3
1.2 Approaches to nanotechnology 4
1.3 Nanotechnology on a large scale and volume 5
1.3.1 Top-down approach 5
1.3.2 Bottom-up approach 6
1.4 Applications 11
1.5 Future considerations 15
1.6 Nanobiomaterials in clinical dentistry 15
References 16
1.1 Introduction
Nanotechnology has been around since the beginning of time. Nature routinely has always used nanotechnology to synthesize molecular structures in the body such as enzymes, proteins, carbohydrates, and lipids which form components of cellular structures. However, the discovery of nanotechnology has been widely attributed to the American Physicist and Nobel Laureate Dr. Richard Phillips Feynman who presented a paper called
"There is plenty of room at the bottom"
in December 29, 1959, at the annual meeting of the American Physical Society at California Institute of Technology. Feynman talked about the storage of information on a very small scale, writing and reading in atoms, about miniaturization of the computer, building tiny machines, tiny factories, and electronic circuits with atoms. He stated that "In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction." However, he did not specifically use the term nanotechnology. The first use of the word "nanotechnology" has been attributed to Tanaguchi in a paper published in 1974 "On the basic concept of nanotechnology." Dr. K. Eric Drexler an MIT graduate later took Feynman's concept of a billion tiny factories and added the idea that they could make more copies of themselves, via computer control instead of control by a human operator, in his 1986 book Engines of Creation: The Coming Era of Nanotechnology, to popularize the potential of nanotechnology.
Several definitions of nanotechnology have since then evolved. For example, the dictionary definition states that nanotechnology is "the art of manipulating materials on an atomic or molecular scale especially to build microscopic devices." Other definitions include the US government which state that "Nanotechnology is research and technology development at the atomic, molecular or macromolecular level in the length scale of approximately 1–100 nm range, to provide a fundamental understanding of phenomena and materials at the nanoscale and to create and use structures, devices and systems that have novel properties and functions because of their small and/or intermediate size." The Japanese have come up with a more focused and succinct definition. "True Nano": as nanotechnology which is expected to cause scientific or technological quantum jumps, or to provide great industrial applications by using phenomena and characteristics peculiar in nanolevel.
It is evident regardless of the definition used that the properties of matter are controlled at a scale between 1 and 100 nm. For example, chemical properties take advantage of large surface to volume ratio for catalysis, interfacial and surface chemistry is important in many applications. Mechanical properties involve improved strength hardness in lightweight nanocomposites and nanomaterials, altered bending, compression properties, and nanomechanics of molecular structures. Optical properties involve absorption and fluorescence of nanocrystals, single photon phenomena, and photonic band gap engineering. Fluidic properties give rise to enhanced flow using nanoparticles and nanoscale adsorbed films are also important. Thermal properties give increased thermoelectric performance of nanoscale materials, and interfacial thermal resistance is important.
1.2 Approaches to nanotechnology
Numerous approaches have been utilized successfully in nanotechnology and as the technology develops further, approaches may emerge. The approaches employed thus far have generally been dictated by the technology available and the background experience of the researchers involved. Nanotechnology is a truly multidisciplinary field involving chemistry, physics, biology, engineering, electronics, and social sciences, which need to be integrated together in order to generate the next level of development in nanotechnology. Fuel cells, mechanically stronger materials, nanobiological devices, molecular electronics, quantum devices, carbon nanotubes (CNTs), etc. have been made using nanotechnology. Even social scientists are debating ethical use of nanotechnology.
The "top-down" approach involves fabrication of device structures via monolithic processing on the nanoscale and has been used with spectacular success in the semiconductor devices used in consumer electronics. The "bottom-up" approach involves the fabrication of device structures via systematic assembly of atoms, molecules, or other basic units of matter. This is the approach nature uses to repair cells, tissues, and organ systems in living things and indeed for life processes such as protein synthesis. Tools are evolving which will give scientists more control over the synthesis and characterization of novel nanostructures yielding a range of new products in the near future.
1.3 Nanotechnology on a large scale and volume
Nanotechnology is being researched extensively internationally, and governments and research organizations are spending large amounts of money and human resources on nanotechnology. This has generated interesting scientific output and potential commercial applications, some of which have been translated into products produced on a large scale. However, in order to realize commercial benefits far more from lab-scale applications need to be commercialized, and for that to happen nanotechnology needs to enter the realm of nanomanufacturing. This involves using the technologies available to produce products on a large scale, which is economically viable. A nanomanufacturing technology should be:
• capable of producing components with nanometer precision,
• able to create systems from these components,
• able to produce many systems simultaneously,
• able to structure in three dimensions,
• cost-effective.
1.3.1 Top-down approach
The most successful industry utilizing the top-down approach is the electronics industry. This industry is utilizing techniques involving a range of technologies such as chemical vapor deposition (CVD), physical vapor deposition (PVD), lithography (photolithography, electron beam, and X-ray lithography), wet and plasma etching to generate functional structures at the micro- and nanoscale (Figure 1.1). Evolution and development of these technologies have allowed the emergence of numerous electronic products and devices that have enhanced the quality of life throughout the world. The feature sizes have shrunk continuously from about 75 m to below 100 nm. This has been achieved by improvements in deposition technology and more importantly due to the development of lithographic techniques and equipment such as X-ray lithography and electron beam lithography.
Techniques such as electron beam lithography, X-ray lithography, and ion beam lithography, all have advantages in terms of resolution achieved; however, there are disadvantages associated with cost, "optics," and detrimental effects on the substrate. These methods are currently under investigation to improve upon current lithographic processes used in the integrated circuits (IC) industry. With continuous developments in these technologies, it is highly likely that the transition from microtechnology to nanotechnology will generate a whole new generation of exciting products and features.
A demonstration of how several techniques can be combined together to form a "nano" wine glass (Figure 1.2). In this example, a focused ion beam and CVD have been employed to produce this striking nanostructure.
The top-down approach is being used to coat various coatings to give improved functionality. For example, vascular stents are being coated using CVD technology with ultrathin diamond-like carbon coatings in order to improve biocompatibility and blood flow (Figure 1.3). Graded a-SixCy: H interfacial layers results in greatly reduced cracking and enhanced adhesion.
1.3.2 Bottom-up approach
The bottom-up approach involves making nanostructures and devices by arranging atom by atom. The scanning tunneling microscope (STM) has been used to build nanosized atomic features such as the letters IBM written using xenon atoms on nickel (Figure 1.4). While this is beautiful and exciting, it remains that the experiment was carried out under carefully controlled conditions (i.e., liquid helium cooling, high vacuum), and it took something like 24 h to get the letters right. Also the atoms are not bonded to the surface just adsorbed and a small change in temperature or pressure will dislodge them. Since this demonstration, significant advances have been made in nanomanufacturing.
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Excerpted from Nanobiomaterials in Clinical Dentistry by Karthikeyan Subramani, Waqar Ahmed, James K. Hartsfield Jr.. Copyright © 2013 Elsevier Inc.. Excerpted by permission of Elsevier.
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