Direct 4D Printing of a Deployable Polymer Wave Spring

Abstract

Abstract 4D printing is now commonly defined as a targeted evolution of a 3D printed structure to change its shape, properties, and functionality over time. In direct 4D printing this targeted evolution is embedded in the structure during the 3D printing process. A heat stimulus can be used to trigger a transition between two states of a printed shape memory polymer. 3D and 4D printing have greatly expanded the design space of a variety of engineering parts. However, 3D printed parts often show anisotropic behavior due to layering, especially when using fused filament fabrication. Here, it is shown how direct 4D printing on a fused filament fabrication system can be used to create deployable polymer wave springs. By introducing a pattern of multimaterial bilayer actuators into the wave spring, it can be printed flat and deployed to a designed spring shape through a thermal stimulus. This method eliminates the typical layering issues found in 3D printed springs due to printing at angles. Additionally, it reduces the print time and support material consumption. These findings show the great potential of direct 4D printing on 3D printers using fused filament fabrication to create functional, 4D printed components with complex geometry, such as polymer springs.