Graphics Reference
In-Depth Information
Evan Malone joined our lab at Cornell shortly after the irst robot appeared
in the
The New York Times
. His goal was to print a robot that would walk out
of the printer. Long before addressing any technical challenges, Evan had to
address a different kind of challenge: none of the commercial printers avail-
able at the time would allow people outside the company to explore new
materials. 3D printing companies closely guarded their patented materials
and any attempt to use unauthorized materials would result in loss of war-
ranty. Moreover, no reasonable researcher would stick active materials into a
$100,000 machine only to see it jam up and stop working.
The quest to explore new materials unconstrained by existing commercial
printer limitations (technical constraints and contractual restrictions) inspired
the Fab@Home project (and to some extent also the RepRap project) and a
series of open “hackable” 3D printer platforms that followed. Simple, low-cost
DIY printers are more open to innovation and less of a tragedy to their user
if they stop working.
Evan loaded a 3D printer with the relevant materials and quickly ran into
the irst snag: the anode material, zinc powder, turned into a paste and did not
want to low through a syringe tip. The harder he pushed, the more it resisted.
When that problem was overcome using various soaps and gels, Evan faced
his next challenge. In most batteries, the recipe calls for a separation layer
made of paper; even the commercial batteries you have at home likely have
a paper layer separating the anode and cathode materials (that's the cheese
between the two slices of bread). The separation layer can't be just any mate-
rial—it has to be semi-permeable, allowing ions to low through but not elec-
trons. Paper is perfect, yet ironically, we could print almost anything, but not
paper. After a few months of experimentation, Evan discovered a recipe for a
printable separation layer made of a certain kind of gel.
Armed with a new recipe and ive different materials, Evan printed a variety
of batteries. Although their energy capacity was approximately one-half of
optimized industrial batteries of equivalent size, their geometry was entirely
custom. He could now print batteries in any shape he wanted, for example, in
the shape of a leg for use as part of a robot.
Printing actuators—active material systems that can move—is even more
challenging. We've printed electro-active polymer actuators, wax actuators,
