The seminal concept of printing multi-functionality can be
traced back at least two decades to the experiments described
in [14], where a two-part polyurethane foam was cast to form
a preferred packaging for existing electronic components.
This process was patented in 1994 [15] and in 1996 with funding
from the Defense Advanced Research Projects Agency
(DARPA) and demonstrated the repackaging of the components
of a personal computer for divers into a case conformal
to the leg of a diver and waterproof to 100 feet [16]. Subsequently,
the research led to the creation of improved algorithms
for optimization of these integrated processes [17].