4D Printing with Photoactive Shape-Changing Polymer

4D打印是一种将3D打印与智能材料相结合的新兴添加剂制造技术。当将热、压力、磁场或水分施加到智能材料上时，4D打印对象可以随时间(第四维)改变其形状。目前的3D打印技术可以打印具有多种材料的对象；然而，这些对象是静态的、几何永久性的，不适合多功能使用。使用光响应变形材料的4D打印是有益的，因为光是无线的，很容易控制，并导致智能材料的快速形状变化。该奖项支持基础研究，以产生合成新型光活性变形聚合物(智能材料)所需的知识，并将这种智能材料集成到使用3D打印过程(熔丝制造)打印的对象中。4D打印对象是可编程的，可以适应其环境。因此，它们可以找到更广泛的应用，包括可折叠的无人机、人造肌肉、夹爪、生物医学药物输送系统、支架和微创手术。研究的目的是：(1)找出偶氮苯变形聚合物颗粒的化学组成与其物理特性(热、机械和光学性能)之间的关系；(2)了解聚合物组成和挤出工艺参数对挤出过程中产生的聚合物长丝的力学性能的影响；以及(3)了解使用不同聚合物组成和挤出工艺参数生产的长丝对4D打印物体的形状变化行为。为了实现第一个目标，将使用差示扫描量热法、UV-Vis光谱和偏光显微镜来测量聚合物微球的热和光学性质。聚合物颗粒还将被浇铸到标准测试棒中，通过应力-应变实验、紫外线照射引起的应力和硬度测量来测量其机械性能。为了实现第二个目标，将改变挤出参数(温度、材料流量和压力)，并测量生产的聚合物长丝的机械性能。为了实现第三个目标，将使用用不同聚合物成分和挤出工艺参数生产的长丝来打印对象。这些打印对象的体积收缩百分比、可逆性、弯曲速度、弯曲角度和机械功输出(在施加应力的一段时间内的形状变化)将在不同级别的光输入(强度)下进行测量。从这项研究中获得的知识可以用于开发使用光活性智能材料的其他4D打印工艺(如立体光刻和选择性粉末烧结)。

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.