here's a book he wrote... 18 years ago. there's great stuff in there. how to build a computer out of rod logic. how get pure sources of elements by cascading filters... armatures for assembling individual atoms.

http://www.amazon.com/Nanosystems-Molecular-Machinery-Manufa...

Richard Feynman apparently had recursive ideas, use a lathe to make a tiny lathe, use the tiny lathe to make a really really tiny lathe... all the way down.

This is the future... but probably a long way away.

I doubt a lego-scale model would help much, the forces and effects involved at the molecular scale are much different. However, K. Eric Drexler, father of the field of molecular nanotechnology, has done some theoretical work to show that it's feasible in his book "Engines of Creation". A newly revised version of it is available for free as an eBook: http://www.wowio.com/users/product.asp?BookId=503

A more technically oriented book is "Nanosystems": http://www.amazon.com/Nanosystems-Molecular-Machinery-Manufa...