Computational Design of 4D Printed Tunable Pneumatic Valves

<br/>4D printing is commonly defined as the targeted evolution of a 3D printed structure to change its shape, properties, and functionalities. This targeted evolution is achieved by utilizing different 3D printing techniques, stimuli, materials, interactions, and modeling approaches. 4D printing greatly enhances the design space of 3D printed structures giving engineers the possibility to create highly integrated and reconfigurable structures. Especially in complex structures such as valves, 3D and 4D printing have the potential to offer significant improvements. Valves are essential parts of almost any pneumatic, hydraulic or other pressurized system. They fulfill a variety of tasks from pressure regulation to flow control and emergency backup systems. Currently, valves are often made from a variety of materials such as plastics and metals, often consisting of multiple parts that require assembly and tuning before system integration. Here we show a fully integrated 4D printed tunable pneumatic pressure release valve, which can be fabricated in one piece requiring no further assembly. The valve is modeled in a top-down approach, the build room for the valve is determined based on commercially available pneumatic pressure release valves. All parts of the valve are fabricated out of related photopolymers using Stratasys PolyJet printing technology. The valve can be manually released through bistable actuation and the release pressure can be tuned prior to fabrication using a numerical optimization scheme. Tunability is achieved by manipulating the geometry and material distribution in parametrized wave and bar springs. Relevant spring parameters and properties are determined through numerical simulations and mechanical testing of 3D-printed, physical prototypes. This concrete example illustrates several possible approaches to how 4D printing can be utilized to retain functionality and performance while minimizing weight and eliminating assembly time in highly integrated additively manufactured systems.