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Aug. 20, 2004 – Last year, father and son team Mark and Dan Ratner published a brief overview of nanotechnology, its science and business potential. “Nanotechnology: A Gentle Introduction to the Next Big Idea” was among a handful of mainstream publications that attempted to explain the foreign and often bizarre nanoscale world to non-technical readers.
It benefited from the expertise of Mark Ratner, a chemist at Northwestern University and a longtime nanotech researcher.
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The slim book served as an appetizer, offering a taste of the whys and how’s that separate nanomatter from its bulk brethren. Richard A.L. Jones, a physicist at the University of Sheffield in the United Kingdom, has expanded the menu with “Soft Machines: Nanotechnology and Life.”
He offers a rich and satisfying full-course meal that incorporates some homegrown ingredients, including his efforts to understand and mimic nature’s recipe for molecular machinery.
He focuses on how we might engineer nanotechnology in the wet world of biology, politely debunking the possibility of miniature submarines patrolling bloodstreams or flying nanobots clogging the airways in the process.
But be forewarned: This is not nano lite. “Soft Machines” is clearly and thoughtfully written, but the subject matter is inherently dense. By Chapter Five you’ll be twisting through the mechanisms behind molecular recognition and protein folding, but only if you had remained attentive in earlier chapters.
Jones begins by explaining two fundamental properties that dictate what happens in a watery environment at the nanoscale: constant motion and stickiness. Those key behaviors explain why the rigid machinery imagined by what Jones terms radical nanotechnologists can’t function in biological settings, and why the “soft machines” he proposes can. (He counts himself among the radicals, but disagrees about what is feasible.)
A close inspection of water molecules at room temperature shows the molecules perpetually jiggling and bouncing into their neighbors, a feature known as Brownian motion. When matter is reduced to the nanoscale, it becomes mostly surface area. Surfaces tend to become attracted to one another, leading to stickiness.
“Imagine mending your bicycle in the shed one day. … The parts are rigid, and if we screw them in place they stay where we put them. Mending a nano-bicycle would be very different.
“The parts would be floppy, and constantly flexing and jiggling about. Whenever different parts touched there would be a high chance that they would stick together. Also, the pile of screws we left in a pot would have jumped out by themselves and would be zigzagging their way toward the garage door,” he writes.
Brownian motion and stickiness will flummox designers bent on building machines that mirror the stiff macro-world, Jones argues.
Mother Nature, instead, recognized these properties could be an asset as she tinkered with what became primitive life and eventually the multi-cellular us. In the watery world of a cell, for instance, the constant movement of molecules and their tendency to stick allows proteins and other valuable “parts” to bump against each other. Some glom together. Those with a tight fit, akin to a lock and key, stay united despite the constant jarring of Brownian motion.
Scientists dubbed the interaction molecular recognition. Complementary shapes lock together, often providing some function when they do. When nature builds its equivalent of a bike, Jones contends, it wants the screws bouncing around haphazardly. Brownian motion ensures that they eventually will land into a suitable hole.
Molecular recognition also plays a large role in self-assembly, the bottom-up approach for building nanoscale objects. Many biological molecules self-assemble, and nanotechnologists already have devised self-assembly methods for making functional materials. But Nature has added a twist to the process, one that Jones and his research team at Sheffield are exploring.
Sometimes the act of one molecule latching onto another molecule puts in motion a cascading set of conformational changes. Proteins, whose function is related to shape, may fold or unfold into a different pattern; for instance, the change may open or shut a cellular passage.
“This simple idea — that a protein changes its own shape when another molecule binds to it — underlies much of the operation of life’s soft machines,” Jones writes, and provides a model for how bionanotechnology might succeed.
“Soft Machines” will be available in the U.K. in August and in the U.S. in September. It is Jones’ second collaboration with Oxford University Press, which published the textbook “Soft Condensed Matter” in 2002.