Eric Drexler’s vision of self-assembling nanoscale machines will be difficult to achieve because of low Reynolds numbers, ubiquitous Brownian motion, and strong surface forces, says physicist Richard Jones of the University of Sheffield.

As an alternative way to achieve “radical nanotechnology,” he proposes two methods: using biological components, such as molecular motors and incorporating them into artificial nanostructures; and bionanotechnology, using some of the design methods of biology and applying them to synthetic matter.