Nature has been working at the level of atoms and molecules for millions of years, so why don't we?
- Richard Feynman
What is Nanotechnology
Nanotechnology is when you work with the matter at scales between ~1 nanometer (nm) to ~100 nm. For example, human hair has ~80,000 nm, bacteria has ~1,000 nm and the width of DNA has ~2.5 nm. Where 1 nm is equal to ~2 atoms. The majority of biology takes place at the nanoscale. Which has a lot of interesting implications and a positive(hopefully exponential) slope in front of us. We are starting to see some interesting developments with companies like Science, co-founded by Max Hodak(previous President of Neuralink). Where Science is starting to leverage what sounds like a bottom-up approach to engineering nano-structures to begin programming parts of the brain starting with cranial nerves.
We’ll be covering the basics of nanotechnology like quantum effects on nano-scale objects, tools of the trade, fabrication processes and examples of nanomaterials.
Surface Area and Quantum Implications
Nanotech is already widely used in places like integrated circuit fabrication or making materials of all kinds have improved properties in repelling, absorbing, filtering and adhesion. When you work with things this small there begins to be different implications that arise. Surface area and quantum effects are two.
Surface area
Nano-sized particles have more potential surface area that can be covered than larger objects all while having the potential to maintain strength. Like the amount of surface area sand can cover on a beach vs an equal amount of sand in the form of gravel spread as thin as possible. This allows nano-materials to be more chemically reactive or be better catalysts. Catalysts are substances that facilitate chemical reactions without being consumed.
Quantum
At the nano-scale gravitational forces become negligible and electromagnetism, strong nuclear force and weak nuclear force become more noticeable. Quantum effects include wave-particle duality, quantum confinement, quantization and quantum tunneling. Nano-particles positions are decided by wave-particle duality. The specific arrangements of atoms can confine the random motion of electrons. Where random motion can be as much as the size of the particle. In the quantum world, continuous becomes discrete. Not all energies or locations are possible. Quantum tunneling is when an electron can travel through a barrier. The electron has to have lower energy than the height of the barrier.
Nano-materials
Nano-materials can be categorized as organic (contains carbon) or inorganic (does not contain carbon). Carbon nano-materials contain strong electrical, thermal and mechanical properties. Carbon can polymerize at the atomic level. With man-made incidental nano-materials like smoke or engineered nanomaterials like carbon nanotubes.
Nano-material dimensions
Nano-material dimensions are decided by the number of sides that are on a scale greater than 100 nm. For example, a 1-dimensional nano-material has 1 side out of three that is greater than 100 nm while 2 are still on a nano-scale. Zero dimensions would be a nano-particle.
0-Dimensions: all sides < 100 nm. Nano-particles.
1-Dimension: 1 side > 100 nm. Wires/tubes/rods.
2-Dimensions: 2 sides > 100 nm. Films and coats.
3-Dimensions: 3 sides > 100nm. No longer nano.
Material Dimensions Table
The material dimensions table shows (in)organic materials grouped into dimensions with a brief description of the dimensions’ characteristics.
Carbon allotropes
Allotropes are when a chemical can exist with the same makeup but in a different structure. Carbon allotropes include graphene, graphene nanoribbons (GNR), carbon nanotubes (CNT) and buckminsterfullerene (buckyball/fullerene). Graphene is a single sheet of graphite(pencil lead). Strongest known material. Flakes are used in a lot of different applications. Cut graphene into specifically sized strips and you have GNRs. Role graphene into a tube and you get CNTs; this isn’t how CNTs are made though. Fullerene is a hollow structure made up of 12 pentagonal and 20 hexagonal faces with a .7 to 1 nm diameter.
Nano-Composites
In addition to nano-materials and allotropes, you also have composites. Composites are typically non-nano materials with nanomaterials mixed in.
Nano-polymers
A polymer is a large molecule made up of repeating smaller molecules called monomers. A copolymer is a polymer with multiple types of monomers. Some common types of polymers are conductive polymers and block copolymers. Conductive polymers contain at least 1 nm of metallic material. Block copolymers are grouped together chains of copolymers. Usually has a soluble block and insoluble block with the insoluble block acting as a shell. Like a drug with a hydrophilic layer and a hydrophobic center like a drug release.
Microscopes
Humans can roughly distinguish up to .2 millimeters apart; about 2 sheets of paper. Light microscopes are the ones you would use in a school lab and are limited to seeing visible light(b/w 400nm-700nm); these are still pretty powerful though. The diffraction limit of visible light is ~200nm or typically a max of 2000x magnification. Nano-scale microscopes have two main types of microscopes. Microscopy is mainly used for imaging and spectroscopy is used for analysis.
Microscopy
Microscopy has two main types of microscope technologies which are Electron Beam Microscopes (EBM) and Scanning Probe Microscopes (SPM). Some of the most common beam microscopes include the Scanning Electron Microscope (SEM) which measures 1-20nm and Transmission Electron Microscopes (TEM). Some of the most common probe microscopes include the Scanning Tunneling Microscope (STM) and the Atomic Force Microscope (AFM).
Spectroscopy
The main focus is to measure spectra. Spectra is the characteristic wavelengths of electromagnetic radiation. Spectra is used to detect, determine, or quantify the molecular or structural composition of a sample. Each type of molecule and atom will reflect, absorb, or emit electromagnetic radiation in its own characteristic way. Some of the most common methods of spectroscopy include X-Ray Diffraction, Ultraviolet-Visible (UV-Vis) Spectroscopy and Ramen Spectroscopy.
Nano-fabrication
Nano-fabrication includes top-down (removal of material) and bottom-up (assemble piece by piece).
Top-down
The top-down approach typically has high energy consumption, potentially toxic chemicals, excess waste; however, this method is highly scalable. Some of the most common ones are X-ray Diffraction, Ultraviolet-Visible (UV-Vis) spectroscopy, and Raman Spectroscopy.
Photo Lithography
Photo Lithography is like creating a shadow on a wall by shining a light through a pattern. You take a source of radiation like light, x-ray, electron beams, and ions. A mask(your pattern) is placed over a substrate. The substrate then gets worn down by the radiation where the mask isn’t protecting it.
UV-light Lithography
X-Ray Lithography
Electron Beam Lithography
Ion-Beam Lithography
Soft Lithography
Scanning Probe
Bottom-up
The bottom-up approach can be more accurate and produces much less waste. Scaling can be difficult though.
Dip Pen Lithography(DPL)
Vapor Deposition
Self-Assembly
Conclusion
Nanotechnology is just reaching the beginning of its innovation S Curve. We will be seeing innovations related to biology, medicine, 3D printers that print at the building blocks of life, and more.