  Vine robots are a class of soft continuum robots that grow via tip eversion,
allowing them to move their tip without relying on reaction forces from the
environment. Constructed from compliant materials such as fabric and thin,
flexible plastic, these robots are able to grow many times their original
length with the use of fluidic pressure. They can be mechanically
programmed/preformed to follow a desired path during growth by changing the
structure of their body prior to deployment. We present a model for fabricating
preformed vine robots with discrete bends. We apply this model across
combinations of three fabrication methods and two materials. One fabrication
method, taping folds into the robot body, is from the literature. The other two
methods, welding folds and connecting fasteners embedded in the robot body, are
novel. Measurements show the ability of the resulting vine robots to follow a
desired path and show that fabrication method has a significant impact. Results
include bend angles with as little as 0.12 degrees of error, and segment
lengths with as low as 0.36 mm of error. The required growth pressure and
average growth speed of these preformed vine robots ranged from 11.5 to 23.7kPA
and 3.75 to 10 cm/s, respectively. These results validate the use of preformed
vine robots for deployment along known paths, and serve as a guide for choosing
a fabrication method and material combination based on the specific needs of
the task.
