  New additive manufacturing methods are needed to realize more complex soft
robots. One example is soft fluidic robotics, which exploits fluidic power and
stiffness gradients. Porous structures are an interesting type for this
approach, as they are flexible and allow for fluid transport. Within this work,
the Infill-Foam (InFoam) is proposed to print structures with graded porosity
by liquid rope coiling (LRC). By exploiting LRC, the InFoam method could
exploit the repeatable coiling patterns to print structures. To this end, only
the characterization of the relation between nozzle height and coil radius and
the extruded length were necessary (at a fixed temperature). Then by adjusting
the nozzle height and/or extrusion speed the porosity of the printed structure
could be set. The InFoam method was demonstrated by printing porous structures
using styrene-ethylene-butylene-styrene (SEBS) with porosities ranging from
46\% to 89\%. In compression tests, the cubes showed large changes in modulus
(more than 200 times), density (-89\% compared to bulk), and energy
dissipation. The InFoam method combined coiling and normal plotting to realize
a large range of porosity gradients. This grading was exploited to realize
rectangular structures with varying deformation patterns, which included
twisting, contraction, and bending. Furthermore, the InFoam method was shown to
be capable of programming the behavior of bending actuators by varying the
porosity. Both the output force and stroke showed correlations similar to those
of the cubes. Thus, the InFoam method can fabricate and program the mechanical
behavior of a soft fluidic (porous) actuator by grading porosity.
