4D printing with shape memory polymers for functional structures and devices
Creators: name: Yang, Chen
Publisher: name: No Publisher Supplied
Year: 2021

description: Additive manufacturing or three-dimensional (3D) printing builds an object through layer-by-layer addition of materials. This additive process greatly advances manufacturing towards complex structures and rapid building. Four-dimensional (4D) printing refers to 3D printing of smart materials whose shape, properties, and functions evolve with time in a programmed way, which produces functional structures and devices spontaneously. Shape memory polymer (SMP) is one kind of smart materials that can maintain a temporarily deformed shape and restore its original shape upon appropriate stimulation. Additionally, SMP also demonstrates modulation in mechanical properties in this process. Despite continuously development of new material compositions, stimulus and printing techniques, field of SMP 4D printing is limited to demonstrating shape-changing capability for visual exhibition, which does not realize full potential in the combination of structural design, 3D printing, and SMP’s shape memory capability and mechanical property modulation. In order to address this limitation and advance the field, this dissertation exploits a rapid and high precision 3D printing technique, projection micro-stereolithography (PµSL), to create SMP structures and devices with designed and task-oriented functionalities. Three projects are included: (1) A SMP hook-and-loop fastener system is designed consisting of a SMP hook patch and a typical loop patch. This fastener system demonstrates tunable adhesion force that is comparable to commercial hook-and-loop fasteners at room temperature and 20 times smaller adhesion force upon heating. (2) A 4D printed transformable tube array (TTA) is created for high-throughput 3D cell culture and histology. The interconnected TTA can be programmed to be expanded by 3.6 times of its printed dimension to match the size of a multi-well plate for 3D cell culture, with the ability to restore its original dimension for transferring all cultures to a histology cassette for sectioning and assessment. Consequently, the TTA enables parallel processing of 3D cell culture and histology to remarkably reduces time and labor cost. (3) 4D printed metamaterials are manufactured with shape reconfigurability, functional deployability and mechanical tunability. Through printing metamaterials using a SMP as the constituent material, mechanical performances of the metamaterials can be tuned dramatically and reversibly by temperature to adapt to requirements. In addition, geometry reconfigurability and deployability of metamaterials are achieved by taking advantage of shape memory capability of the constituent SMP. Through exploring new possibilities in combinations of 3D structural design, 3D printing, and SMP’s two important characteristics: shape memory capability and mechanical property modulation, this dissertation presents 3 works using 4D printing with SMP with expanded functionalities. Eventually, it serves to move the field of 4D printing one step closer towards real-world applications.