80 Nanomedicine In  order  to  build  durable  nanorobots,  we  first  must  be able to fabricate parts made of diamond, sapphire, or simi- lar  strong  materials.  The  controlled  addition  of  carbon atoms to a growth surface of the diamond crystal lattice is called  diamond  mechanosynthesis.  [6;7]  In  2003,  we  pro- posed a new family of mechanosynthetic tools intended to be employed for the placement of two carbon atoms – a CC “dimer” – onto a growing diamond surface at a specific site. [6] These tools should be stable in vacuum and should be able to hold and position a CC dimer in a manner suitable for positionally controlled diamond mechanosynthesis at liquid nitrogen temperatures and possibly even at room temperatures. The function of a dimer placement tool is to position the dimer, then bond the dimer to a precisely chosen location on  a  growing  diamond  molecular  structure,  and  finally  to withdraw the tool, leaving the dimer behind on the growing structure. The diamond structure is then built up, dimer by dimer, until a complete molecularly precise nanopart has been fabricated. Both  the  fabrication  of  nanoparts  and  the  assembly  of nanoparts into working nanorobots must be automated and must employ massive parallelism to be practical. There must be many hands at work simultaneously. Without this parallelism, there would be too many atoms per device (millions/billions) and too many devices needing to be assembled per application (trillions).  New  techniques  for  massively  parallel  positional assembly  are  being  developed,  including  massively  parallel manipulator arrays and self-replicating systems. One example of parallel assembly arrays, called “exponential assembly”, has been proposed and patented by Zyvex [8]. There have also been  many  proposals  for  self-replicating  systems  known  as “molecular assemblers” – tiny machines that could manufac- ture nanorobots with molecular precision [9].