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Incorporating thermoplastic materials with shape memory properties into the fused filament fabrication process enables what is commonly referred to as 4D printing. When the blends are composed of one or more materials with inherent shape memory properties, the tailoring of critical parameters such as shape recovery temperature can be realized. Previous work by our group demonstrated the creation of shape memory polymer blends where one component was elastomeric. The following work entails the development and characterization of rigid polyester blends that are biocompatible and biodegradable in addition to having shape memory properties. Dynamic mechanical analysis (DMA) was used to determine the critical deformation and recovery temperatures. The effect of print raster patterns on the DMA results was also evaluated. Micro- tensile testing was used to characterize the physical properties of the materials at elevated temperatures. Finally, scanning electron microanalysis was used to examine the fracture surfaces of spent tensile specimens. 

Creating 3D printed structures from materials with shape memory properties allows these structures to change form, modifying configuration or function over time in response to external stimuli such as temperature, light, electrical current, etc. This area of additive manufacturing has come to be known as 4D printing. A variety of geometries have been previously explored in the context of 4D printing, including foldable surfaces (e.g. Origami), lattices, and bio-inspired shapes. However, with advances in solid modeling software tools, more sophisticated spatially- varying lattices are now easily generated to further optimize the mechanical performance and functionality of a 4D printed structure. In this work, complex lattices are created to bend at specific locations with intentionally-reduced stiffness and improved compliance based on locally-reduced strut dimensions. By experimentally demonstrating more complex geometries in the study of 4D printing, new applications can be considered that were not previously possible, with tailored performance allowing for balancing between weight and actuation.