Setting Foot in the Ethical Nanoforest

William P. Cheshire, Jr., M.D., Consultant in Neurology
Mayo Clinic

One reason nanotechnology attracts interest is that people are naturally fascinated by unexpected juxtapositions of size. The choice of the term "nanotrees"¹ to describe elongated arborizing molecular structures illustrates the intuitive tendency of the human mind to draw from experience of forms and patterns in the familiar world when evaluating novel structures in the nanoworld. Now that Danish researchers have assembled clusters of carbon nanotubes into "nanoforests,"² one cannot help but ponder what it would be like to be reduced to nanoscale size and walk through a nanoforest in the cool of the day. What wonders might one see and feel?

This nanoforest promenade thought experiment would find a landscape full of surprises. For in the scaling down of linear dimensions, nonlinear relationships of physical forces would make it seem as if the laws of physics had been rewritten. Vision would lack detailed resolution as single photons collided with the entire retina. Colors would translate to tintless, toneless moiré bands of interfering waves. Oxygen molecules would be too large to inhale. No longer would gravity predominate in holding one¹s feet to the ground, but nearby molecules' electromagnetic charges would hurl one to and fro between positive and negative polarities. Occasional pops of static electricity would surge like lightning. Leviathan-like flagella would lash out from lake-sized bacteria. Snowflakes the size of cities would settle onto the nanoforest canopy.

At the nanoscale, plain surfaces become rough and rough places plain. In an apparent reversal of features, the irregular contour of the artificial carbon nanotube forest provides a non-stick workbench for the manipulation of nanosize devices and structures that, because of molecular-level physical properties, would normally adhere to smooth surfaces.²

The nanoworld is, of course, our own world at one level. Our connection to it means that small things can have enormous medical, ethical, and social implications. To reconcile physics and chemistry with the larger world of biology remains one of the most exciting challenges in science. To reconcile what is known of the deterministic world of material interaction with the decisions faced by the larger complex world of human society is an even greater challenge.

Analogies that jump from one scale to another are useful in understanding relationships. Such analogies can also be misleading if conditions and contexts are overlooked. One can get lost in the nanoforest and mistakenly reduce larger meanings to nanoscale ideas. Just as the laws of physics for nanoworld and macroworld phenomena are disproportionate, interactions at the nanoscale incompletely inform perspectives on ethical principles for human society. There are important human goods that cannot be defined by sheer efficiency and vital human values that cannot be apprehended by attention only to necessity.

Appreciation of the multilayered nature of reality is essential to entering into the nanoforest with sure ethical footing. Now more than ever, we must see the forest for the trees.

William P. Cheshire,Jr., M.D. is Consultant in Neurology at the Mayo Clinic in Jacksonville, Florida, and Associate Professor of Neurology at the Mayo Clinic College of Medicine. He is also a Nano & Society Fellow.

References
¹ K. A. Dick, K. Deppert, T. Martensson, W Seifert, & L. Samuelson, Growth of GaP Nanotree Structures by Sequential Seeding of 1D Nanowires, 272 J. Crystal Growth 131-137 (2004).
² K. Gjerde, J. Kjelstrup-Hansen, C.H. Clausen, K.B.K. Teo, W.I. Milne, H-G Rubahn, & P. Bøggild. Carbon Nanotube Forests: A Non-stick Workbench for Nanomanipulation. 17 Nanotechnology 4916-4922 (2006).