Brownian motion and nanotechnology

Brownian motion started when Robert Brown looked into his microscope and observed that pollen suspended in water moved around in a continuous random motion. Wanting to rule out some “vital life force,” Brown also  investigated dead things such as sand and metals but he observed the same jittery motion. The dead danced as well. Or perhaps the Epicureans anticipated the phenomenon of Brownian motion in Lucretius‘s scientific poem On the Nature of Things:

Observe what happens when sunbeams are admitted into a building and shed light on its shadowy places. You will see a multitude of tiny particles mingling in a multitude of ways… their dancing is an actual indication of underlying movements of matter that are hidden from our sight… It originates with the atoms which move of themselves.

The writer Mark Haw has been so fascinated with the phenomenon and history of Brownian motion that he decided to write a book about it called Middle World: The Restless Heart of Matter and Life. This accessible introduction covers the history of Brownian motion, the “mesoscopic” middle world between the (sub)atomic world and the world of “large” objects,  taking us from the puzzling observations of Robert Brown to its relevance for the upcoming science of nanotechnology. Commenting on the challenges that the middle world, where “objects simply cannot  stand still,” presents to Eric Drexler’s vision of  “hard” nanotechnology, the author observes:

Matter in the middle world does things differently.  You could insist on modeling your machines after the macroworld and finding chemical ways to achieve that. But why not use the fantastically rich range of things that matter does in the middle world to come up with whole new ways of solving engineering problems? Why not profit from unavoidable restlessness? We know it can be done: life has already done it.

Although published 3 years earlier than Haw’s book, Richard Jones picks up this very theme in his excellent book Soft Machines: Nanotechnology and Life. This book presents a more technical treatment of Brownian motion and other nanoscale phenomena that an advanced nanotechnology simply cannot work around.  But instead of resisting the unruly world of randomness and sticky objects, Jones proposes to embrace these phenomena as the most obvious road to build nanoscale devices. Although the author does not completely dismiss the “top-down” Drexler approach, he strongly prefers to use the bionanotechnological tools that nature has provided and to improve upon them. He also introduces an approach called “biomimetic nanotechnology” that would involve “the copying of the principles of operation of biological nanotechnology, but executing them in synthetic materials.”

Since August 2004, Richard Jones also publishes a blog that reports on the future of nanotechnology  and has featured informed critiques of the Drexlerian vision of radical nanotechnology and Singularitarianism.

Soft nanotechnology

Ever since humans imagined the ability to deliberately manipulate matter on the atomic scale, they have glimpsed the boundless possibilities of the science of nanotechnology. And for almost as long, they have disputed whether molecular machines should be built using a “hard” (physical engineering) or “soft” (biology-based) approach. On his blog, Richard Jones, author of the book Soft Machines, discusses some of the more intricate details and debates in molecular nanotechnology.

In a recent post, Jones delves into the issue of what lessons nanotechnology should take away from biological systems: should we view cell biology as the penultimate achievement in nanotechnology, or can we improve upon the slap-dash, trial-and-error approach of evolution by making rational choices in materials? In his words:

The engineers’ view, if I can put it that way, is that nature shows what can be achieved with random design methods and a palette of unsuitable materials allocated by the accidents of history. If you take this point of view, it seems obvious that it should be fairly straightforward to make nanoscale machines whose performance vastly exceeds that of biology, by making rational choices of materials, rather than making do with what the accidents of evolution have provided, and by using the design principles we’ve learnt in macroscopic engineering.

The opposite view stresses that evolution is an extremely effective way of searching parameter space, and that in consequence is that we should assume that biological design solutions are likely to be close to optimal for the environment for which they’ve evolved. Where these design solutions seem odd from our point of view, their unfamiliarity is to be ascribed to the different ways in which physics works at the nanoscale. At its most extreme, this view regards biological nanotechnology, not just as the existence proof for nanotechnology, but as an upper limit on its capabilities.

Ultimately, argues Jones, nanotechnology has a lot to learn from biological systems — but that doesn’t preclude the possibility of improving upon it, either. He cites the emerging science of synthetic biology as a field that is using a sensible engineering approach to the development of biological nanodevices such as molecular motors, and wonders if this approach may ultimately lead to a biomemetic nanotechnology.

The right lessons for nanotechnology to learn from biology might not always be the obvious ones, but there’s no doubting their importance. Can the traffic ever go the other way – will there be lessons for biology to learn from nanotechnology? It seems inevitable that the enterprise of doing engineering with nanoscale biological components must lead to a deeper understanding of molecular biophysics. I wonder, though, whether there might not be some deeper consequences. What separates the two extreme positions on the relevance of biology to nanotechnology is a difference in opinion on the issue of the degree to which our biology is optimal, and whether there could be other, fundamentally different kinds of biology, possibly optimised for a different set of environmental parameters. It may well be a vain expectation to imagine that a wholly synthetic nanotechnology could ever match the performance of cell biology, but even considering the possibility represents a valuable broadening of our horizons.

In a more recent post, Jones announces the upcoming Soft Nanotechnology meeting in London next year.

A forthcoming conference in London will be discussing the “soft” approach to nanotechnology. The meeting – Faraday Discussion 143 – Soft Nanotechnology – is organised by the UK’s Royal Society of Chemistry, and follows a rather unusual format. Selected participants in the meeting submit a full research paper, which is peer reviewed and circulated, before the meeting, to all the attendees. The meeting itself concentrates on a detailed discussion of the papers, rather than a simple presentation of the results.