Introduction to Nanotechnology - History, Definition, Methodology, Applications, and Challenges. Instructor: Dr. Yu-Bin Chen Date: 07/25/2012

Transcription

1 Introduction to Nanotechnology - History, Definition, Methodology, Applications, and Challenges Instructor: Dr. Yu-Bin Chen Date: 07/25/2012

2 Outline Outline History Definition Methodology Applications Challenges, Risks, and Ethics 2

3 History Atomic World to the Ancient China 公孫龍 ( 約西元前 ): 一尺之棰, 日取其半, 萬世不竭莊子雜篇天下棰就是木材, 意思是說一條尺把長的木杖, 今天截取一半, 明天截取一半的一半, 依次截取下去, 永遠截取不完 Continuum Assumption: A medium is indefinitely divisible without changing its physical nature. 3

4 Limitations of the Macroscopic Formulation History V Local density lim V 0 m V Constant? Density is not a constant and fluctuates with time even at macroscopic equilibrium. When the dimension is comparable with or smaller than that of the mechanistic length, such as molecular mean free path, the continuum assumption will break down. 4

5 There s Plenty of Room at the Bottom History Why cannot we write the entire 24 volumes of the Encyclopaedia Brittanica on the head of a pin? The Nobel Prize in Physics 1965 by Richard P. Feynman Full contents of the lecture has been downloaded and posted in our website as well. Please read what Feynman could view at the end of 1959 about micro/nanotechnology. Other useful information about micro/nanotechnology can also be found in 5

6 History The Development History of Nanotechnology 1959 Feynman gives after-dinner talk describing molecular machines building with atomic precision 1974 Taniguchi uses term "nano-technology" in paper on ion-sputter machining 1981 First technical paper on molecular engineering to build with atomic precision STM invented 1985 Buckyball discovered 1986 AFM invented 1989 IBM logo spelled in individual atoms 1991 Carbon nanotube discovered 1997 First company founded: Zyvex 2000 President Clinton announces U.S. National Nanotechnology Initiative 2011 First programmable nanowire circuits for nanoprocessors DNA molecular robots learn to walk in any direction along a branched track Mechanical manipulation of silicon dimers on a silicon surface 6

8 Definition Nanometer A nanometre (American spelling: nanometer; symbol nm) is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- (from the Ancient Greek νάνος, nanos, "dwarf") with the parent unit name metre (from Greek μέτρον, metrοn, "unit of measurement"). The nanometre is often used to express dimensions on the atomic scales: the diameter of a helium atom, for example, is about 0.1 nm, and that of a ribosome is about 20 nm. In these uses, the nanometre appears to be supplanting the other common unit for atomic scale dimensions, the angstrom, which is equal to 0.1 nanometre ,756 km 1.3 cm

9 Definition Nanoscale vs. Microscale Dr. Chen s research interests 9 Z. M. Zhang, Nano/Microscale Heat Transfer, 2007.

10 National Nanotechnology Initiative (NNI) Nanotechnology Definition Research and technology development at the atomic, molecular or macromolecular levels, in the length scale of approximately nanometer 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 novel and differentiating properties and functions are developed at a critical length scale of matter typically under 100 nm. Definition Nanotechnology research and development includes manipulation under control of the nanoscale structures and their integration into larger material components, systems and architectures. Within these larger scale assemblies, the control and construction of their structures and components remains at the nanometer scale. In some particular cases, the critical length scale for novel properties and phenomena may be under 1 nm or be larger than 100 nm. 10

11 Limitations of the Macroscopic Formulation Inappropriate definition for temperature: Temperature can only be defined for stable-equilibrium states. That is, extremely high temperature gradient and/or during very short time periods of time, the local equilibrium may be inappropriate. Reduction of thermal conductivity: Thermal conductivity will be reduced for thin films or narrow wires due to boundary scattering. Electron and photon tunneling: Electrons and photons can transport through a very narrow gap. Surface forces superiority: Surface forces scale down with L 2 while the volume forces scale down with L 3. Better catalyst: The large exposing area of nanoscale particles can boost the catalysis. Magnetic storage: The nanoscale Fe, Co, and Ni alloy has strong magnetization ideal for data storage. Definition 11

12 Definition Nanoscience and Nanotechnology Related Journals (66 total) Rank Abbreviated Journal Title I F 1 NAT NANOTECHNOL NANO TODAY ADV MATER NANO LETT ACS NANO ADV FUNCT MATER SMALL NANO RES NANOMED-NANOTECHOL J PHYS CHEM LETT Rank Abbreviated Journal Title I F 11 NANOSCALE NANOTOXICOLOGY LAB CHIP BIOSENS BIOELECTRON WIRES NANOMED NANOBI NANOMEDICINE-UK J PHYS CHEM C ACS APPL MATER INTER J BIOMED NANOTECHNOL NANOTECHNOLOGY ESI Web of Science (2011 Report) 12

13 Definition Nanotechnology Resources in Taiwan 工業技術研究院奈米科技研發中心中央研究院表面奈米科學實驗室中央研究院奈米核心設施國家奈米元件實驗室微系統暨奈米科技協會同步輻射研究中心材料世界網 Nano Science 奈米科學網奈米創新網國科會北區微機電系統研究中心國科會中區微機電系統研究中心國科會精密儀器發展中心奈米技術研究室國科會微機電與奈米技術推動小組台灣大學奈米科技研究中心台灣大學顯微技術與奈米分析中心台灣大學化學工程學系電子與光電陶瓷研究室台北科技大學奈米光電磁材料技術研發中心大同大學奈米材料實驗室清華大學奈米與微系統中心交通大學奈米科技中心華梵大學工學院奈米科技中心中興大學奈米科技研究中心中科園區技術服務中心奈米科技組中正大學奈米科技設計與原型研發中心成功大學微奈米科技研究中心彰化師範大學奈米科技中心中山大學奈米科技研發中心南台科技大學奈米科技研究中心南台灣奈米科技研究中心南區微奈米科技聯盟高屏地區奈米核心設施建造台灣奈米技術產業發展協會 13

15 Methodology Scanning Electron Microscopy (SEM) 15

16 Methodology Transmission Electron Microscopy (TEM) Transmission electron microscopy (TEM) is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera. 16

17 Scanning Probe Microscopy (SPM) Methodology Scanning probe microscopy (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a function of position. SPM was founded with the invention of the scanning tunneling microscope in The SPM has multiple types, including AFM, NSOM(SNOM), and so on. 17

18 Methodology Atomic Force Microscopy (AFM) The AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface. The cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever according to Hooke's law. Typically, the deflection is measured using a laser spot reflected from the top surface of the cantilever into an array of photodiodes. Other methods that are used include optical interferometry, capacitive sensing or piezoresistive AFM cantilevers. 18

19 Methodology Near-Field Scanning Optical Microscopy (NSOM) 19 Near-field scanning optical microscopy (NSOM/SNOM) is a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. This is done by placing the detector very close (distance much smaller than wavelength λ) to the specimen surface. This allows for the surface inspection with high spatial, spectral and temporal resolving power. In particular, lateral resolution of 20 nm and vertical resolution of 2 5 nm have been demonstrated. As in optical microscopy, the contrast mechanism can be easily adapted to study different properties, such as refractive index, chemical structure and local stress.

20 Focused Ion Beam Microscopy (FIB) Methodology Focused ion beam (FIB) systems operate in a similar fashion to a scanning electron microscope (SEM) except, rather than a beam of electrons and as the name implies, FIB systems use a finely focused beam of ions (usually gallium) that can be operated at low beam currents for imaging or high beam currents for site specific sputtering or milling. 20

21 Fabrication of Nanoscale Structures (1/3) 21 Background Fabricating structures at the nano level can be broken down into two main methods; top down and bottom up construction. Top Down Fabrication Top down fabrication can be likened to sculpting from a block of stone. A piece of the base material is gradually eroded until the desired shape is achieved. That is, you start at the top of the blank piece and work your way down removing material from where it is not required. Nanotechnology techniques for top down fabrication vary but can be split into mechanical and chemical fabrication techniques. Top Down Fabrication Techniques The most top down fabrication technique is nanolithography. In this process, required material is protected by a mask and the exposed material is etched away. Depending upon the level of resolution required for features in the final product, etching of the base material can be done chemically using acids or mechanically using ultraviolet light, x-rays or electron beams. This is the technique applied to the manufacture of computer chips. Methodology nomanufacturing.html

22 Methodology Fabrication of Nanoscale Structures (2/3) 22 Bottom Up Fabrication Bottom up fabrication can be likened to building a brick house. Instead of placing bricks one at a time to produce a house, bottom up fabrication techniques place atoms or molecules one at a time to build the desired nanostructure. Such processes are time consuming and so self assembly techniques are employed where the atoms arrange themselves as required. Bottom Up Fabrication Techniques Self assembling nanomachines are regularly mentioned by science fiction writers but significant obstacles including the laws of physics will need to be overcome or circumvented before this becomes a reality. Other areas involving bottom up fabrication are already quite successful. Manufacturing quantum dots by selfassembly quantum dots has rendered the top down lithographic approach to semiconductor quantum dot fabrication virtually obsolete.

23 Methodology Fabrication of Nanoscale Structures (3/3) Advantages Top-down Once Research and Development complete and manufacturing line is complete costs drop Bulk production Bottom-up Self-Assembly processes Less product defects Disadvantages Contamination Machine Cost Complexity Clean room cost and complexity Physical limits Material damage Surface imperfections Heat dissipation Not very robust products Lengthy process to obtain nanoparticles 23

25 Applications Chocolate Self-assembly Making chocolate considered "good" is about forming as many type V crystals as possible. This provides the best appearance and texture and creates the most stable crystals, so the texture and appearance will not degrade over time. To accomplish this, the temperature is carefully manipulated during the crystallization. Crystal Melting temp. Notes I 17 C (63 F) Soft, crumbly, melts too easily II 21 C (70 F) Soft, crumbly, melts too easily III 26 C (79 F) Firm, poor snap, melts too easily IV 28 C (82 F) Firm, good snap, melts too easily V 34 C (93 F) Glossy, firm, best snap, melts near body temperature (37 C) VI 36 C (97 F) Hard, takes weeks to form 25

26 Smart phone Applications A smartphone is a mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a feature phone.the first smartphones mainly combined the functions of a personal digital assistant (PDA) and a mobile phone or camera phone. Today's models also serve to combine the functions of portable media players, low-end compact digital cameras, pocket video cameras, and GPS navigation units. Modern smartphones typically also include high-resolution touchscreens, web browsers that can access and properly display standard web pages rather than just mobile-optimized sites, and high-speed data access via Wi-Fi and mobile broadband. 26

27 Applications Cosmetics In cosmetics there are currently two main uses for nanotechnology. The first of these is the use of nanoparticles as UV filters. Titanium dioxide (TiO2) and Zinc oxide (ZnO) are the main compounds used in these applications. Organic alternatives to these have also been developed. The second use is nanotechnology for delivery. Liposomes and niosomes are used in the cosmetic industry as delivery vehicles. Newer structures such as solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) have been found to be better performers than liposomes. In particular, NLCs have been identified as a potential next generation cosmetic delivery agent that can provide enhanced skin hydration, bioavailability, stability of the agent and controlled occlusion. Encapsulation techniques have been proposed for carrying cosmetic actives April%2009.pdf

28 Applications Morpho 28 Many Morpho butterflies are colored in metallic, shimmering shades of blue and green. These colors are an example of iridescence: the microscopic scales covering the Morpho's wings reflect incident light repeatedly at successive layers, leading to interference effects that depend on both wavelength and angle of incidence/observance. Thus the colors produced vary with viewing angle, however they are actually surprisingly uniform, perhaps due to the tetrahedral (diamond-like) structural arrangement of the scales or diffraction from overlying cell layers. This structure may be likened to a photonic crystal. The lamellate structure of their wing scales has been studied as a model in the development of fabrics, dye-free paints, and anti-counterfeit technology used in currency.

29 Applications Carbon Nanotube (CNTs) High tensile strength (~63 GPa) >> High-carbon steel (1.2 GPa) High elastic modulus (~ 1 TPa) High thermal conductivity along the nanotube (6000 W/m/K) >> Copper (385 W/m/K) High electrical current density for armchair nanotubes (~1000 times that of metals) 29

30 Accplications Multifunctional Nanowire Bioscaffolds A simple and inexpensive way to create a nanowire coating on the surface of biocompatible titanium has been developed. The technique could be used to create more effective surfaces for prosthetics, such as hip replacements, as well as in dental reconstruction and vascular stents. The material can also be easily sterilised using ultraviolet light and water or ethanol, which means it could safely be used in hospitals. 30 Chem. Mater. 2007, 19,

31 Applications Moore s Law The number of transistors per square inch on integrated circuits double every year. "..(T)he first microprocessor only had 22 hundred transistors. We are looking at something a million times that complex in the next generations a billion transistors. What that gives us in the way of flexibility to design products is phenomenal." Gordon E. Moore,

32 Applications Lotus Effect The lotus effect refers to the very high water repellence (superhydrophobicity) exhibited by the leaves of the lotus flower (Nelumbo). Dirt particles are picked up by water droplets due to a complex micro- and nanoscopic architecture of the surface, which minimizes adhesion. The hydrophobicity of a surface is related to its contact angle. The higher the contact angle the higher the hydrophobicity of a surface. Surfaces with a contact angle < 90 are referred to as hydrophilic and those with an angle >90 as hydrophobic. Plants with a double structured surface like the lotus can reach a contact angle of 170 whereas a droplet s actual contact area is only 0.6%. All this leads to a self-cleaning effect. 32

33 Applications Fuel Cells Catalysts are used with fuels such as hydrogen or methanol to produce hydrogen ions. Platinum, which is very expensive, is the catalyst typically used in this process. Companies are using nanoparticles of platinum to reduce the amount of platinum needed, or using nanoparticles of other materials to replace platinum entirely and thereby lower costs. Fuel cells contain membranes that allow hydrogen ions to pass through the cell but do not allow other atoms or ions, such as oxygen, to pass through. Companies are using nanotechnology to create more efficient membranes; this will allow them to build lighter weight and longer lasting fuel cells. Researchers at Rensselaer Polytechnic Institute have investigated the storage of hydrogen in graphene (single atom thick carbon sheets). Hydrogen has a high bonding energy to carbon, and the researchers used annealing and plasma treatment to increase this bonding energy. 33

35 Challenges, Risks, and Ethics Challenges, Risks, and Ethics 1. Monitoring the exposure of nanoscale engineered to humans in the air and within water. The challenge becomes increasingly difficult in more complex matrices like food. 2. Developing and validating methods to evaluate the toxicity of engineered nano-materials. 3. Constructing models for predicting the potential impact of engineered nano-materials on the environment and human health. 4. Educating people about the pros and cons for nanotechnology Defining areas applicable to nanotechnology with regulations and laws. Overemphasized functions of nanotechnology should be prohibited.