What happens if the room at the bottom runs out? A close look at small water pores

Atalk by Richard Feynman, ``There is plenty of room at the bottom,'' was given >40 years ago at the California Institute of Technology during the annual meeting of the American Physical Society. Today, in the context of nanotechnology, this lecture is frequently cited because of its remarkable visionary power. Very early, Feynman envisaged nanotechnology as a whole new field and argued that a wealth of revolutionary technological advances and applications, like ultra-high density data storage media or ultra-small mechanical devices, would be feasible, with much room for improvements until finally fundamental physical limits at the atomic scale become relevant. To illustrate how much room there actually is at the bottom, Feynman asks us to imagine a miniaturization contest in which one participant manages to write on a pinhead ``how's this?'' Her competitor returns it, and in the dot of the ``i'' it says, ``not so hot,'' and so on.

The field has seen remarkable achievements since then, indeed, most notably the reduction of the area of transistors in microelectronic circuits by more than a factor of 10⁷, or of the space required to store 1 bit of information on a magnetic surface by ≈10⁸. Nanomechanical devices have seen tremendous progress, too, through impressive advances in scanning probe microscopy (1, 2).

But what if the room at the bottom actually runs out? What if the physics like that appears at the limit of miniaturization? In their molecular dynamics study in a recent issue of PNAS, Beckstein and Sansom (3) address this question for the water flow through a short hydrophobic nanopore, where the fluid is essentially confined to one dimension (Fig. …