The Doors of perception website has posted a transcript of Neil Gershenfeld’s presentation on the work of MIT’s centre for Bits and Atoms.
“a paintable computer, a viscous medium with tiny silicon fragments that makes a pour-out computer, and if it’s not fast enough or doesn’t store enough, you put another few pounds or paint out another few square inches of computing.”
» Doors7: Neil Gershenfeld: “This is the revolution for us”
[via Andrew Otwell]
Petafloptimism 
Random thoughts:
Clay might work better from the standpoint of building up layers. You can also use it before it’s dry.
Stucco sounds like a good compromise.
Also consider mixing in photoelectrics and painting/siding the outside of something.