STUFF MATTERS: Chapters 9-11 (the end)

CHAPTER 9: REFINED
• On ceramics
• Some properties of ceramics noted by the author:
o Relatively chemically inert and not degraded by UV [because it does not absorb UV?]
o Impervious to scratching
o Non-stick surface except for tannins and a few others which can be removed by bleach or acid
o Material strength
• Because of these properties, the author thinks that “for real sustainability, we must look to ceramics”.
• Because of its high melting point ceramics cannot be melted and poured unlike metals, plastics, and glass.
• Clay is a mixture of small mineral crystals and water.  Terra cotta is made from clay containing mostly quartz, alumina, iron hydr/oxide crystals (thus the red color).
• FIRING OF CERAMICS:  In turning clay into pottery, it is first heated at high temperatures causing the water to evaporate.  Further heat applied is absorbed by atoms in the crystal resulting in more kinetic energy.  Atoms on the surface of crystals with extra nonbonded electrons “jump” back and forth between unoccupied spots in adjacent crystals.  Eventually, they form stable bonds to another atom on the surface of the next crystal, forming bridges between the crystals until the mixture achieves the more cohesive structure of a single material.  For terra cotta, the temperature required are relatively low and can be provided by a wood fire.
• GLAZING:  In the East, glazing was invented to make the outside surface of ceramic pottery more waterproof.   “Ash” is applied on the surface of the ceramic which then turns into a glass coating after firing. Glazing, however, did not eliminate the issue of porosity which weakens the ceramics and makes them vulnerable to cracking when heated.
• THE MAKING OF PORCELAIN:  Experimentations done by the Chinese during the Eastern Han Dynasty led to the discovery of the use of the white mineral kaolin, which when added to clay along with other minerals like feldspar and quartz, led to a type of white ceramic with vastly improved properties.  This white ceramic did not attain its special properties unless fired to a very hot 1300 Celsius.  This white ceramic, now called porcelain, had the following properties:
o A very smooth surface
o Stronger and tougher than any other known ceramic
o It could be made very thin because of its strength
• In the words of the author, “porcelain came to represent the perfect marriage of technical skill and artistic expression”.  The discovery of porcelain brought much pride to the Han Dynasty that royal dynasties throughout Chinese history came to be associated with different types of imperial porcelain.  As he noted, porcelain was a physical manifestation of “how much more technically advanced the Chinese were than anyone else in the world” during this era.
• In 1704, the British “discovered” the process used by the Chinese to create porcelain which had remained a secret, discovering a local source of kaolin and achieving the high temperature (1350 C) needed to fire the correct mixture to produce, 50 years later, their version of “bone china porcelain”.

CHAPTER 10: IMMORTAL
• On artificial implants
• The material used for body casts (for immobilizing broken parts) (called plaster of Paris) is made by adding water to dehydrated gypsum (hydrated calcium sulfate) and letting it dry and harden like cement.
• AMALGMA DENTAL FILLING:  Amalgam, an alloy composed of tin, silver, and mercury used as dental filling, was invented in 1804.  The mercury in the mixture (acts like a solvent for the other metals?) keeps the alloy liquid at room temperature.  Upon reaction with the other components (the author does not mention what they are), a reaction takes place that causes the entire mixture to harden and mechanically bond to the tooth.
• COMPOSITE RESIN DENTAL FILLING:  This resin composite filling is made from a mixture of transparent plastic and silica powder, which, upon exposure to UV light, hardens into wear-resistant filling the color of natural tooth.
• TITANIUM:  This metal is one of the few metals that can be tolerated by the body for use as structural replacement or screws.  It also is notable for its ability to osseointegrate, forming strong bonds with real bone.  It is strong, light, and chemically inert which makes it an ideal material.  The titanium oxide that forms on its layer helps retain the structural health of the entire metal.
• REPLACEMENT JOINTS:  The internal surfaces of joints are very susceptible to wearing because they are dependent on lubricating fluid and cartilage to prevent damaging friction between bone surfaces due to constant motion and weight-bearing.
• Hip joint replacements using ivory was first attempted in 1891.  Presently, ceramic and titanium are used.  High density polyethylene is used as the artificial cartilage to line the newly drilled pelvis socket as a protection against friction from the mobile titanium ball.  The fit can be made quite perfectly in some cases that the artificial cartilage is not needed.
• TISSUE ENGINEERING:  In the 1960’s, Professor Larry Hench discovered the mineral hydroxyapatite that was found to bond to bone strongly.  They used this material to produce a porous, bioactive “glass” with tiny channels in which osteoblasts (bone cells) embed themselves as they grow new bone, breaking down the bioglass in the process.
• 3-D PRINTING:  This very new technology has been used to manufacture objects using printer technology with metals, glass, plastic, etc. as the “ink”.  In , Professor Alex Seifalian and his team created a 3-D copy of a patient’s windpipe.  They built a scaffolding in which mesenchymal stem cells taken from the patient are embedded.  This was then placed in a bioreactor to grow an exact replica of the windpipe.  Using the patient’s own stem cells to grow the replica windpipe avoids transplant rejection by the body.   Two issues still need to be resolved for this to be a viable transplant process:  1) developing tissue integration for blood supply to the artificial portion and 2) sterilization method that does involve high temperatures (the scaffolding is a polymer that cannot withstand high temperatures).

CHAPTER 11: SYNTHESIS
• Our material world is composed of “complex expressions of human needs and desires” and materials science is the way by which humans try to understand and “master the complexity of the inner structure” of these materials.  “It is no less significant, no less human, than music, art, film, or literature, or the other sciences, but it less well known.”
• This inner structure is not apparent from the sometimes monolithic, homogeneous appearance of many of these materials.  The most fundamental of these inner structures is, of course, the atom but at the larger scales, materials scientist see “dislocations, crystals, fibers, scaffolds, gels, and foams” despite how shiny or cohesive a material may look.
• Useful note:  94 different types of atoms exist naturally on earth.  8 of these make up 98.8% of the mass of the earth (iron, oxygen, silicon, nickel, magnesium, sulfur, calcium, and aluminum), with carbon only making up a trace. All the gold ever mined would fit inside a large house.
• THE IMPORTANCE OF STRUCTURE OVER ATOMIC COMPOSITION FOR DETERMINING PROPERTIES:  The author makes the point that the rarity of technologically useful elements like neodymium or platinum may not turn out to be a big problem because as we have seen in the case of graphite versus diamond, atomic composition is not the only determinant for a material’s properties; structure plays a very significant, sometimes, overriding role.  In this topic, the author offers a simplified explanation of the basis for understanding structure in material:
o “These structures are not arbitrary – you cannot create any structure – but are governed by the rules of quantum mechanics, which treat atoms not as singular particles but as an expression of many waves of probability.  (This is why it makes sense to refer to the atoms themselves as structures, as well as their formation when they bond with one another.)  Some of these structures create electrons that can move, and this results in a material that can conduct electricity.  Graphite has such a structure, and so conducts electricity.  Exactly the same atoms in a diamond but in a different structure do not allow the electrons to move so easily within the crystal, and so diamonds do not conduct electricity.”
• THE MATERIALS SCIENCE DICTUM:  Plumbing the depths of this structure is the primary work of materials scientists:  “It is hard to overestimate the philosophical as well as the technological importance of this dictum of materials science: that knowing the basic chemical composition is not enough to understand materiality.”
• NANOSCALE LEVEL UNDERSTANDING AND MANIPULATION:  These unique characteristics of materials stemming from the atomic composition and structure first make themselves known at the nanoscale level (a nanostructure consists atoms in the hundreds) and “it is manipulations at this scale that will affect their properties”.
• The author gives the following example illustrating that this level of material manipulation has been going on for hundreds of years (they just were not aware of it back then):  “When a blacksmith hits a piece of metal, he or she is changing the shape of metal crystals within it by “nucleating” nanoscale dislocations – in other words, by causing the transfer of atoms from one side of the crystal to the other at the speed of sound.”
• NANOSCALE:  Nanostructures have been manufactured that can collect light and store it as electricity or create light sources or even sense smells.  They can also self-assemble because of strong electrostatic and surface tension forces at this scale (gravity is a weaker force acting on a car). Nanoscale self assembly is already taking place in the molecular machinery of cells.
• MICROSCALE
o THE SILICON CHIP:  The silicon chip is an example of a microscopic size object ten to a hundred times bigger than a nanostructure.  Although they have no moving parts, they use electric and magnetic properties to direct the flow of information.
o BIOLOGICAL CELLS:  Cells also exist at the microscopic level but is composed of hundreds of nanostructures.  [Its operation relies on interactions between these nanostructures.]
o SUGAR CRYSTALS AND COCOA GRAINS IN CHOCOLATE:  Manipulating at this scale allows more control over the texture and taste of chocolate.
o INVISIBILITY SHIELDS:  The design is based on manipulating how microstructures within an object (meta-materials) refract light by designing them with variable refraction indices.  When this object is formed like a shield and wrapped around an object, they can bend light in such a way that the object shielded is not visible from whichever direction it is viewed.
• MACROSCALE:  The atomic scale, nanoscale, and microscale then grow into the macroscale structure of a material.  It is at this level, that all the different underlying structures come together to form a cohesive, strong, smooth, and optically dynamic material.  The author used the example of the touch screen of a tablet or smartphone which appears flawlessly smooth but is in fact composed of tiny pixels of liquid crystals whose colors can change so fast that a movie appears smooth and continuous.  Porcelain is another good illustration of this jump to macroscale.
• MINIATURE SCALE:  Combining the atomic, nano, micro, and microstructures to a size just visible to the naked eye:  hair strand, needle, thread, 12-size font etc.  At this level, regular thread and Kevlar would appear the same.  “It is at this scale that our sense of touch engages with materials.”
• HUMAN SCALE:  The scale at which we can hold stuff in our hands.
• THE REAL CHALLENGE:  To connect structures designed starting from the atomic scale in a way that they can intelligently interact with each other to form a macroscopic human-sized object, wired-up internally with nanoscale electronics that can act as its nervous system.  The author imagines such an object being able to produce its own energy, modulate and distribute where it is needed and repair itself, just like “living materials” like us.   The author points out:
• “One of the biggest questions in science is whether communication between the scales combined with active responses is a sufficient explanation of what makes something alive”.  [This segueways well to the next prospective book on my reading list:  Life’s Ratchet].
• RELATIONSHIP BETWEEN THE LIVING AND THE IMMATERIAL AND MATERIA WORLD:  “What makes us human, though, is not just the physical materiality of our bodies, synthetic or not.  We inhabit an immaterial world, too: the world of our minds, our emotions, and our perceptions.  But the material world, although separate, is not entirely divorced from these worlds – it strongly influences them…This is because for humans, materials are not just functional…(Materials) mean something, they embody our ideals, they give us part of our identity.”
• The author ends the chapter as well as the book by condensing the essence of materials science and the two-way relationship between us and our stuff in the following statement:  “…Materials are a reflection of who we are, a multi-scale expression of our human needs and desires” and in the same way, the materials that we choose to grace our bodies and our homes and those that we choose to surround us in the workplace, in the cities, in the world say a lot about who we are as humans and as individuals.

THE END