4D Printing with Photoactive Shape-Changing Polymer

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4D printing is an emerging additive manufacturing technology that combines 3D printing with smart materials. The 4D printed objects can change their shape over time (the 4th dimension) when applying heat, pressure, magnetic field, or moisture to the smart materials. Current 3D printing technology can print objects with a multitude of materials; however, these objects are static, geometrically permanent, and not suitable for multi-functional use. 4D printing with a light responsive shape-changing material is beneficial because light is wireless, easily controllable, and causes a rapid shape change of the smart material. This award supports fundamental research to generate knowledge needed for synthesis of a novel photoactive shape changing polymer (smart material) and integrating this smart material into objects printed using a 3D printing process (fused filament fabrication). 4D printed objects are programmable and can adapt to their environment. Therefore, they can find wider applications, including foldable unmanned aerial vehicles, artificial muscles, grippers, biomedical drug delivery systems, stents, and minimally invasive surgeries. The research objectives are: (1) to find the relationship between chemical composition of azobenzene shape changing polymer pellets and their physical characteristics (thermal, mechanical, and optical properties); (2) to understand how polymer's composition and extrusion process parameters affect mechanical properties of polymer filaments produced by the extrusion process; and (3) to understand the shape change behavior of 4D printed objects using filaments produced with different polymer composition and extrusion process parameters. To accomplish the first objective, differential scanning calorimetry, UV-Vis spectroscopy, and polarizing light microscopy will be used to measure thermal and optical properties of the polymer pellets. Polymer pellets will also be casted into standard testing bars to measure their mechanical properties through stress-strain experiments, stress induced by UV light exposure, and hardness measurements. To achieve the second objective, extrusion parameters (temperature, material flow rate, and pressure) will be altered, and mechanical properties of produced polymer filaments will be measured. To achieve the third objective, objects will be printed using filaments produced with different polymer composition and extrusion process parameters. Percentage volume contraction, reversibility, bending speed, bending angle, and mechanical work output (shape change during a period of time over which stress is applied) of these printed objects will be measured with different levels of light input (intensity). The knowledge gained from this research can be useful in developing other 4D printing processes (such as stereolithography and selective-powder-sintering) using photoactive smart materials.