Until recently, humankind’s skill at molecular manipulation was nothing compared to nature’s. Witness the precisely fabricated tissues
of the human body, the intricate chemical control system of the genome, or
the hair-like locomotive structure of a paramecium -- each a tour de force
of biological complexity and precision.
Now, however, chemists and materials researchers have begun
to learn some of nature’s tricks, and are adding
a few of their own.
Broadly speaking, their research is proceeding along two
fronts: mimicking nature’s products, and mimicking
nature’s methods. A good example of the first
type is the work of Nicholas Kotov and his colleagues at
Oklahoma State University, where they have developed a material similar
to the mother-of-pearl lining found in seashells. Also called
nacre, the natural form of this iridescent, white substance
is renowned by materials scientists for its strength and
flexibility, which derive from a structure that is densely
layered at the nanoscale. The artificial nacre shows promise
for use in the manufacture of lightweight, rigid composites
for aircraft parts, body armor or artificial bone.
Another good example is the work of Samuel
Stupp and his team at Northwestern University, where
they have developed a series of molecular scaffolds resembling
the structures of bone, nerves and other tissues. Each
type of scaffold starts out as a gel of nanoscale molecular
fibers that can be injected into the site of a broken bone,
say, or a severed nerve. Once in place, the fibers will
spontaneously assemble themselves into a biocompatible
matrix that will speed and guide the body’s natural
healing process.
Meanwhile, in the effort to mimic nature’s methods,
we clearly have a lot to learn. Our current industrial
methods for making molecules and materials typically involve
some combination of heat, pressure, exotic raw materials,
dangerous solvents and undesirable by-products. Yet living
organisms can usually make what they need at ambient temperature
and pressure using little more than air and water, plus some
organic compounds derived from their food. Can we do as well?
Among the leaders in the effort to answer this question are Angela
Belcher and her colleagues at MIT, who are trying to emulate
the biological processes that give rise to materials like shell
and bone. To do this, they create a matrix of natural or artificial
protein molecules, which in turn provide a template for inorganic
compounds, such as calcite, to deposit themselves in a precisely
ordered array of crystals at the nanoscale. Depending on the
precise composition, this nanostuctured material can then be
used in a wide variety of electronic, magnetic and structural
applications.
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