Invisible Architecture

The NanoWorld of Buckminster Fuller

by Bonnie Goldstein DeVarco



V. Molecular Architecture - Carbon, Meet Silicon

Silicon -- Natural Forms, Ancient Uses

Silicon. If you think about this word for a moment, maybe the first thing that would come to mind is Silicon Valley, the geographic heart of the computer industry. Or perhaps in your mind's eye you could see a clear gel, or a silicon chip. Maybe you imagine a nebulous manmade material used in the manufacture of our common but still new technologies such as solar cells, batteries or transistors and semiconductors. Rarely do we think about silicon as a simple and natural element in the world around us: sand on the beach, black clear remnants of a volcanic eruption, or essential domestic artifacts like the transparent pane occupying the nearest window frame or the glass you drink from at each meal. We don't link silicon to its fundamental presence in the ancient art of glass-making, one of the oldest technologies found in the earliest civilizations of Egypt and Babylonia. And how many of us would think about silicon as the main element comprising the sharp, strong obsidian blades or arrowheads in humans' most ancient tools?

As common as silicon is in today's world, many of us would be surprised to learn that it is the second most abundant element on earth, making up almost a third of the earth's crust, and the main ingredient in even the tiniest grains of sand or the hardest samples of natural glass and quartz crystals. But it can be said, with its myriad applications, that this nonmetallic element has almost single handedly redefined our notion of "machine" in the second half of this century, rapidly becoming an increasingly transparent, weightless, ephemeral analogue of human life. Even so, we still closely guard our outmoded concept of machines as hard, and hollow metallic shells or cold crankshafts, solid, smooth pistons and notched metal gears, connotations which continue to weigh down and polarize the relationship between humans and their technologies.

Carbon -- The Basis of Life

"The carbon in our body originated in space. Indeed, we now know that it was ejected from some star a long, long time ago and then was reprocessed and ended up on the Earth's biosphere. What is absolutely fascinating and certainly something that excited me when I first discovered it, is that every one of us is made of carbon, therefore every one of us is made of stardust... "One thing they are not so sure of is what is the form of that dust, what is the structure. How does the carbon nucleate to form these that form these little wudges that go on to grow into planets?" 36   Harold Kroto

Carbon, known now in its three forms, graphite, diamond and buckminsterfullerene, is the basis of organic chemistry, the fundamental element of all biological life as we have come to know it. Yet carbon is closer to silicon than to any other single element. Referred to in high school chemistry labs as "kissing cousins," carbon and silicon have more similarities in their respective properties and structures than differences. Because of the placement on the periodic table, each containing four electrons in their outer shells, they are found right next to each other in the same vertical family. Because of their tendency to easily bond with other elements, both can be found or combined into numerous other forms.

It is easy to compare these two abundant elements so central to everyday life. Although silicon is only slightly more metallic than carbon because it tends to lose electrons more easily, it is safe to say that silicon is considered inorganic while carbon is organic. If we wanted to compare carbon with silicon as analogues of the animate and inanimate world, we need only look to their molecular structures and the functions they fulfill.

The three allotropes of carbon: diamond, graphite and buckminsterfullerene37 exhibit many of the same structural characteristics as various forms of silicon. These three pure forms of carbon vary from one another by the crystal structure the atoms take. It is possible to compare each with a form of silicon that has similar properties or fulfills similar functions in our everyday world. For the purposes of this qualitative comparison, graphite's analog could easily be mica, diamond's analog, quartz crystal and buckyball's could be silicones or even the recently discovered silicon-60.

Silicon and Carbon -- A Comparison

Graphite, the simplest form of pure carbon, is so soft it can be cleaved at any point. Each atom is bonded to three others forming layers of flat sheets of hexagons which can easily slide back and forth over one another. Mica, a mineral containing atoms of silicon, aluminum and oxygen (S02) also has a flat hexagonal structure and can be easily cleaved into thin sheets like graphite.

Graphite is one of our most common communication tools, its name meaning "to write." It is soft and "greasy" so it can easily be used to lubricate moving machine parts. Mixed with clay, graphite forms the "lead" in pencils, simple instruments each of us have held since our earliest years in school. Its longevity, as well its ability to be erased lends pencil lead nicely to marks on paper artifacts. This gives graphite an intrinsically functional and lasting value in the varied manuscripts and documents found in every archives in the world. Graphite, like mica also has many industrial uses.

Diamond is the strongest natural substance known, is often used to grind and polish other materials to the finest degree. A precut diamond can be identified by its octahedral outer shape and its atoms are arranged in a dense, tetrahedral framework or lattice. Each carbon atom of diamond is the center of one tetrahedron and the vertex of another. By the same token, quartz crystal's molecular structure is a also a dense and strong tetrahedral network. Although not as hard as diamond, quartz's crystalline structure is very similar to it. In addition, while diamonds are formed in molten lava by the heat and pressure deep in the earth, obsidian, a form of silicon, is the hard black glass formed of lava when it meets oxygen and hardens in the outer atmosphere.

Diamonds come from the core of the Earth. They are the strongest and most aesthetically valuable crystals known to man which are used symbols for lasting love and the bonds of marriage as well as for drill bits used to dig deep into earth and cut through the hardest materials. Quartz crystal is also one of the hardest minerals. Its conductivity enables an electric current to ride through this beautiful silicon-based quartz crystal. Both diamond and crystal have been used liberally for tools used in making lenses for microscopes and telescopes.

Buckminsterfullerene, the most recently discovered allotrope of pure carbon, is a hollow cage molecule with flexibility and strength, exhibiting perfect spherical symmetry. Buckminsterfullerene's 60 atoms are bonded together in a stable, yet flexible hexapent cage. Its most unique property is that it can be bonded both from the inside and the outside. Silicon and oxygen combine to form silicones, a cross between organic materials such as oil, rubber and plastics and inorganic materials such as sand, glass and quartz crystal. Buckyballs on the other hand, also carry structural characteristics of both the organic fivefold world and the inorganic crystal world. The links in the molecular skeleton of alternating silicon, oxygen and other atoms in silicones have bond strength about one and a half times as great as the carbon bond that holds organic molecules together, thus giving them organic properties such lubrication, water repellence and flexibility, the same properties of buckyballs. Both buckyballs and silicones both form polymers.

Buckyballs are just beginning, in theory and in their first real applications, to revolutionize the already existing computer industry. They will soon be used as superconductors, components of tiny batteries, lubricants, "beads" in nano-sized abacuses for computer information coding and as essential components of soon-to-be-seen "optical tweezers," nanoprobes of the atomic scale. Fullerenes may soon become models for a new generation of microscale machines. In medicine and in the body, water-soluble fullerenes may someday replace the tiniest components of our cellular make-up, such as microtubules in the brain's neurological structure. Because of the cage-like structure, buckyballs may someday contain and dispense with viral material that grow and breakdown cells of the body through cancer or HIV.37 Silicones, the most flexible materials when used in rubber-like compounds, have myriad applications in various technologies. They are often used in the body as well.

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