Foams are ubiquitous, being used in applications such as padding, insulation, and noise isolation.
Bonding different density foams together produces undesired stress concentrations and boundary
effects. Creating controlled gradients in foam properties has been a challenge for traditional and
AM processes. Here we show how to use a form of material extrusion called Viscous Thread
APrinting (VTP) to produce foams with multiple stiffnesses and continuous gradients between
different stiffnesses. We do so by varying the path speed during extrusion to control the
production of microstructures. We compare the process of producing discrete components and
those with gradients, showing that those with gradients have higher strength in plane during
tension, have no discontinuities in out of plane stiffness, and are less prone to forming cracks at
the boundaries. We demonstrate the process in thermoplastic polyurethane (TPU).Mechanical Engineerin
