ABOUT THE NANOTECHNOLOGY DEMONSTRATION KIT
―If I were asked for an area of science and engineering that will most likely produce the breakthroughs of tomorrow, I would point to nanoscale science and engineering.‖
Assistant to the President for Science and Technology
former Director of the National Science Foundation
Terms such as nanoscience, nanotechnology, nanoengineering, nanoscale materials and nanocomposites have become quite popular in recent years, often appearing on the evening news. Yet there seems to be little to connect this emerging field to fundamental secondary science education curriculum. A nanometer is one billionth of a meter, about the size of a few atoms lined up next to each other. Nanoscience and nanotechnology refer to things that occur on the nanometer scale (1 to 100 nanometers). In the same way that 100 yards is the relevant scale for a football game, the nanoscale is the playing field for molecules and their interactions.
―Nanotechnology has given us the tools…to play with the ultimate toy box of nature – atoms and
molecules.‖ -Horst Stormer, Nobel Laureate
Phenomenal examples of nanotechnology abound in nature (abalone shells, photosynthesis, the human body). The capability for humans to manufacture materials using similar principles, will change the way almost everything is designed and manufactured, including vaccines, computers, water filters, batteries, paint, and more fuel-efficient cars. Physicists, biologists, chemists, materials scientists, and engineers are working together in research laboratories across the country to build nanoscale materials to make lighter, faster, stronger and smarter products.
The purpose of this Nanotechnology Demonstration Kit is to allow secondary school students to learn about nanotechnology and next generation materials by making and testing nanostructured materials by themselves using a minimum of laboratory supplies and ordinary tap water. The transfer of nanoscience concepts is often significantly limited by the high cost and complexity of the required scientific instrumentation, such as scanning tunneling microscopy and molecular beam epitaxy. Electrostatic self-assembly (ESA) is a revolutionary processing technique that, unlike other state-of-the-art methods to synthesize nanostructured materials and microelectronic devices, involves only low-cost lab supplies and simple processing at room temperature and pressure, in an open environment.
The kit is divided into five units that will introduce students to the following concepts.
； Nanotechnology and nanostructured materials
； Chemical bonding
； Electrostatic self-assembly
； Fabrication of their own nanostructured film
The activities provide examples of the concepts introduced and relate them to everyday uses. A set of questions is included for each activity to encourage further thought. During the ESA fabrication experiment, layers that are one molecule (a few nanometers) thick are built up one at a time, and stacked on top of each other to form a film. The stacking is observed through the increase in the bright color (violet or orange) of the film. This is related back to concepts introduced during previous units.
TABLE OF CONTENTS UNIT ONE: INTRODUCTION TO NANOTECHNOLOGY .................................................. 1 INTRODUCTION TO NANOTECHNOLOGY ........................................................................................ 1
WHAT IS NANOTECHNOLOGY 1
NANOTECHNOLOGY SCIENCE 2
EXAMPLES OF NANOTECHNOLOGY 2
MANUFACTURING METHODS 3
FUTURE APPLICATIONS: 3
ONE NANOTECHNOLOGY PROCESS - ELECTROSTATIC SELF ASSEMBLY 4 BACKGROUND SCIENCE FOR NANOTECHNOLOGY AND ESA ........................................................ 5
UNITS AND MEASURES 5
ELECTROSTATICS REVIEW 5
ATOMS, MOLECULES AND CHEMICAL BONDS 6
UNIT TWO: INTRODUCTION TO ELECTROSTATIC SELF-ASSEMBLY ..................... 8 INTRODUCTION TO ELECTROSTATIC SELF-ASSEMBLY ................................................................ 8
DEVICE DESIGN 8
SUBSTRATE PREPARATION 8
SOLUTION PREPARATION 9
SELF ASSEMBLY - MONOLAYER FORMATION 9
PARTICIPATORY DEMONSTRATION OF ESA ............................................................................... 10
CONCEPTS TO INVESTIGATE: 10
EXERCISE 2.1: PREPARING ‗SOLUTIONS‘ 10
EXERCISE 2.2: FORMATION OF A SIMPLE ESA FILM 11
EXERCISE 2.3: USING ONLY ANION MOLECULES 12
EXERCISE 2.4: SUBSTRATE CONTAMINATION 13
EXERCISE 2.5: MIXING THE ANION AND CATION SOLUTIONS TOGETHER 14 UNIT THREE: MAKE YOUR OWN NANOSTRUCTURED MATERIAL ........................ 15 MANUFACTURE AN ESA FILM ON A MICROSCOPE SLIDE ........................................................... 15
EXERCISE 3.1: PREPARING SOLUTIONS 15
EXERCISE 3.2: MANUFACTURE AN ELECTROSTATIC SELF-ASSEMBLED FILM 16
EXERCISE 3.3: USING ONLY THE ANION 18
EXERCISE 3.4: SUBSTRATE CONTAMINATION 19
EXERCISE 3.5: MIXING THE ANION AND CATION TOGETHER 20
NOTES FOR THE TEACHER 21
INVESTIGATE OTHER APPLICATIONS FOR NANOTECHNOLOGY .................................................. 22
UNIT ONE: INTRODUCTION TO NANOTECHNOLOGY
Introduction to Nanotechnology
The objective of this module is to introduce the concept and definitions of Nanotechnology. This unit is intended as a lecture or discussion and should be used as a refresher on topics assumed to have been addressed in previous learning activities, such as:
； Electrostatics – the attraction and repulsion of like and opposite charges
； Chemical bonding – definition of atoms, molecules and polymers and a simple understanding
of ionic and covalent bonds.
； Surface tension
What is Nanotechnology
Nano - one billionth of something. Derived from the Greek word for dwarf.
Technology – Systematic scientific and engineering knowledge related to manufacturing. Knowing how to make something and why it works.
Meter (m) - a length that is approximately 39 inches
Nanometer (nm) - one billionth of a meter
Nanotechnology – knowing how to manufacture things at the nanometer scale, the size of atoms.
Like all other technologies it relies on many branches of science, in particular chemistry and physics. Nanotechnology is similar to other technologies in that the better the science is understood, the better the technology can be used and the better the devices that can be made.
Nanotechnology differs from other low and high technologies in the premise. Nanotechnology is manufacturing things by extracting raw materials from the environment and assembling them an atom or molecule at a time.
This would compare to what we would call a low technology activity such as sculpting. A sculptor will extract the raw material in the form of a large rock. The parts of the rock that are not part of the sculpture are removed and discarded using chisels and files. The artistic skill of the sculptor determines how well any cracks or color variations in the stone are incorporated into the final artwork.
An example of high technology is the manufacture of computer microchips. A large rod of silicon passes through multiple purification steps to remove the impurities that present the challenge to the sculptor. Once this is refined to satisfaction the large rod is cut into wafers. Piles of various chemicals called photoresists are layered on the wafer. These piles are then etched or modified with lasers, the chisels and files of the high technologists. These tools are able to etch
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with a resolution at 250 nanometers. The goal in this industry is to improve the tools to reduce this resolution to 100 nanometers by the year 2006.
In nanotechnology the required atoms are extracted from a chemical soup and assembled into the desired material or device. This is similar to constructing a word from letters floating in a bowl of alphabet soup, with the letters analogous to atoms.
A second concept that is central to nanotechnology is self-assembly. The atoms are too small for a person to direct, find, and place each atom individually. A template needs to be developed that stores the plans, like DNA in our body. A process needs to be developed that finds the correct atoms and places them according to the template.
There are many laws and principles that have been around since the start of the universe. These laws have not changed or been modified. Our classification and understanding of these laws is constantly being improved and revised. This is the work of the scientist whether the field is astronomy, physics, chemistry or biology. The science required for nanotechnology development and applications will draw from all scientific disciplines but most heavily chemistry, physics and biology.
Nanotechnology will not change or append any scientific laws. It will force us to expand and modify our understanding of these laws and how we can use them. The uses for the new materials and devices can be for beneficial purposes as well as for malicious purposes and can have unintended effects. The ethical and legal aspects of nanotechnology are a serious discussion in the nanotechnology community but we will not pursue that discussion any further.
Examples of Nanotechnology
Our physical bodies are amazing Nanotechnology machines. We feed our bodies food, water and air. The body converts these raw materials into a variety of amino acids, sugars and minerals. From these materials DNA, cells, blood, muscle, bones etc are all created. Other processes convert these inputs into energy that is used to power our bodies.
One example biologists are studying is how the abalone forms its shell. The shells are 98% calcium carbonate and are 3000 times tougher than rocks made from the same material. The mollusk forms the shell by alternating very thin layers, 50 to 200 nanometers, of calcium carbonate and proteins. Biologists have attempted to manufacture a new material by mimicking the materials and structure of the abalone shell. They have succeeded in making a material with good toughness characteristics, but not nearly as good as the abalone‘s, which is still at least 10 times tougher. The hypothesis is that thinner layers than the biologists could make are needed. To truly succeed the biologists will need to be able to control their manufacturing at a molecular level, nanotechnology. (Biomimetics is a relatively new branch of biology that is attempting to create new materials by mimicking biological processes like the abalone.)
Photosynthesis is an example of a process that extracts carbon dioxide from air and water from the plant to rearrange the atoms to form oxygen and carbohydrates using sunlight for energy.
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There are many more examples in nature. The important attributes are that the starting materials are rearranged and recombined to give products with completely different properties. In the example of photosynthesis chemical reactions are involved, in the example of abalone shells a physical structure was modified.
Nanotechnology is an emerging technology. This means that we can imagine more fantastic things than we can accomplish today. Some people have achieved control over the placement of individual atoms. Others have generated computer simulations of 3 dimensional atomic scale pumps and motors that follow the laws of chemistry and physics. Others have created processes that accomplish part of the total objective.
Today, Scanning Tunneling Microscopy can accomplish true atomic position control. This is a device used to look at atoms and take a picture of atoms. It is also able to pick up and place one atom at a time. The first demonstration of this was to write IBM by placing Xenon atoms on a Nickel substrate. This device is used for research and for high technology art. If it were automated it could self assemble. However it is too slow to build any significant quantity of material. Remember it would take 2 billion years to make 0.6 ounces of water at 10 million molecules a second.
Today Electro-static self-assembly accomplishes partial self-assembly and molecular control in one dimension. We will investigate this process further in later sections of this module.
Many creative people are working hard to develop the vision, the science, the technology and the tools required for nanotechnology. The visions they have for devices to be made by nanotechnology affect all aspects of our lives. Some examples include
- Information on a thousand CDs could fit into a wristwatch
- Many medical procedures could be handled by nano-machines that scour and rebuild arteries, rebuild bones, reinforce bones with diamond thread.
- Nanostructured vaccines that are more precisely manufactured to eliminate the hazards of today‘s vaccines, nano-machines that build an independent immune system that is not disabled by AIDs.
- Manufacturing will use less material, will reuse more garbage, will require fewer toxic molecules for manufacture and create no pollution.
- Planes, trains and automobiles will be lighter, faster, and more fuel-efficient; constructed of lighter, stronger materials.
- Inexpensive solar cell sheets that can be handled like fabric. Smart fabric that opens microscopic windows when the inside temperature reaches a certain degree and humidity could be self-powered by lights or the sun.
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One Nanotechnology Process - Electrostatic Self Assembly
There are many different processes being investigated to make devices using nanotechnology. We will explore in more detail one of these processes, Electrostatic Self-Assembly (ESA).
ESA is a process that applies a coating exactly one molecule thick on a surface. By building a coating one molecule thick at a time absolute control of the composition can be achieved.
The ESA process in a nutshell is the creation of a charged surface and the bonding of oppositely charged ions to the surface. The electrostatic forces on the ions drive and control the layer to one molecular thickness while creating the next charged surface. The devices that can be made are limited by the imagination and the ability to identify suitable ions for deposition.
Following is some of the science background needed to understand this corner of nanotechnology.
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Background Science for Nanotechnology and ESA
Units and measures
Just how small is the nanotechnology world?
Distance Dimension visualization
Distance to sun = 150 billion m 1 meter = 1 billion nm
Distance to moon = 380 million m 1 Pinhead = 1 million nm
Height of Mt Everest = 8.8 thousand m 1 Red blood cell = 5 thousand nm
Height of Michael Jordan = 2 m 1 DNA molecule = 2.5 nm
1 Foot = 0.3 m 1 Sodium atom = 0.2 nm
Just how many atoms have to be handled to build a device one atom at a time?
Avogadro number visualization
1 gram-mole = Number of atoms in 18 grams Avogadro number of unpopped popcorn 23(0.6 ounce) of water = 6.02*10 (Avogadro kernels = a pile that covers the entire United
number) States 9 miles deep
Time to count every atom in a gram-mole =
2 billion years at a rate of 10 million atoms
Time for a 1 gigahertz computer to count
every atom in a gram-mole at one atom per
cycle (Hz) = 20 million years
(Note it is assumed that previous investigations into electrostatics have been performed. If not there is a section in Appendix 3 that addresses electrostatics in more than summary form.)
Like charges repel and unlike charges attract
When a balloon is rubbed on a wool sweater it will be attracted enough to a wall to stick. When two balloons are rubbed on a wool sweater they will be repelled by each other enough to move away if hung on a string.
The force that pushes the balloons away is an electrical repulsion. The act of rubbing transfers loose electrons from the wool sweater to the balloon by friction, giving the balloon a net negative charge. When two balloons are rubbed together they both pick up extra electrons to create a negative charge on both balloons. The negative charges try to get away from each other and the balloons will push away from each other.
The force that holds the balloon to the wall is an electrical attraction. The act of rubbing transfers loose electrons from the wool sweater to the balloon by friction, giving the balloon a net negative charge. The wall has a net positive charge. As long as the balloon holds enough electrons it will hang on the wall.
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The physical response of two oppositely charged materials is always an attraction of the two charges. In some cases the attraction is strong enough to move or make objects stick, like balloons, hair and static cling socks . In other cases the attraction is strong enough to cause electrons to jump, like lightning or static shock when touching a doorknob.
Atoms, Molecules and Chemical Bonds
All materials are made of atoms. All atoms are composed of protons, neutrons and electrons. Protons have a positive electrical charge, neutrons have a neutral electrical charge and electrons have a negative electrical charge. The number of protons and electrons in an atom are equal making atoms electrically neutral.
Molecules are atoms that are held together by chemical bonds. The number and location of the protons and electrons in the molecule are equal making them electrically neutral.
Polymers are a special kind of molecule made by bonding repeating smaller molecules (monomers). For example, bonding in a long chain made of ethylene molecules makes polyethylene.
Polar molecules occur when the electrons and protons are not always evenly distributed around the molecule. Water is a ―polar‖ molecule; this means that even though there is the same number of protons and electrons in the whole molecule there is a partial negative charge on the oxygen and partial positive charges on the hydrogen.
O ; ; H H
Illustration of the polar character of water
The polar character of water causes the waters molecules to be attracted to each other. The partial negative charge on the oxygen is attracted to the partial positive charge on the hydrogen.
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H H H HO O
H O H
O H O H H H H O O
Illustration of the polar cohesion between individual water molecules
An ion is an atom or molecule that has a net positive or negative charge.
An anion is an atom or molecule with a negative charge, more electrons than protons
A cation is an atom or molecule with a positive charge, more protons than electrons.
Ionic bonds are when one atom or molecule donates one or more electrons to another atom or molecule. This creates one positive ion and one negative ion. The attraction of the two charges holds the atoms or molecules together.
Electrostatic forces hold ionic bonds together.
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