3D Printing of Smart Structural Composites by Thermoelectric Extrusion with Molecular Precision

智能结构复合材料提供具有内置传感（温度、压力、流量和负载）功能的结构支撑。智能基础设施的最新进展以及可穿戴设备和智能假肢的激增，催生了对制造价格合理、可定制且精确的智能结构复合材料的需求。在目前的制造方法中，3D打印可以直接从计算机模型中构建可定制的部件，但缺乏加入提供传感功能的添加剂（如压电纳米颗粒）的能力。大多数基于聚合物的3D打印方法都是通过从喷嘴中挤出超过其熔化温度的聚合物逐层沉积来构建零件，并且在冷却时对聚合物微观结构的控制有限。与传统制造工艺制造的零件相比，这导致3D打印零件的尺寸精度较差。该奖项支持在3D打印领域创造新知识的基础研究，其在医疗保健、教育和工程领域的应用将促进新的经济活动。该奖项还支持女性和未被充分代表的群体参与工程研究，并支持调查人员与初高中学生的联系。本研究的目的是制定热塑性离聚物/压电复合材料挤压过程中的外加电场与材料性能之间的关系（例如，光学清晰度，强度，压电应变系数以及聚合物基质和纳米颗粒之间的界面粘附性）。在热塑性离聚体中，碳氢链和离子基团之间的极性差异产生静电驱动力并导致离子聚集。在这种情况下，存在一个知识缺口的热塑性离聚体的离子聚集在其熔融温度以上的外部施加的电场的影响下。为了了解电场（大于聚集的静电力）如何影响热塑性离聚体/压电添加剂的混合物的聚集形态（尺寸，在基体和纳米级添加剂周围的分布），研究团队将对具有代表性的热塑性离聚体与压电添加剂（乙烯/甲基丙烯酸与PZT-5H和PVDF）进行实验研究和粗粒度分子动力学模拟。

A smart structural composite provides structural support with built-in sensing (temperature, pressure, flow and load) functionalities. Recent advances in intelligent infrastructure and the proliferation of wearable gadgets and smart prosthetics have created a need for manufacturing affordable, customizable, and precise smart structural composites. Among current manufacturing methods, 3D printing can directly build customizable parts from computer models, but lack the ability to incorporate additives (such as piezoelectric nanoparticles) that provide sensing functionality. Most polymer-based 3D printing methods build parts by layer-by-layer deposition of a polymer extruded out of a nozzle above its melting temperature and have limited control of the polymer microstructure as it cools down. This leads to poor dimensional accuracy of 3D printed parts in comparison with parts fabricated from traditional manufacturing processes. This award supports fundamental research to create new knowledge in 3D printing and its application in healthcare, education, and engineering will foster new economic activity. This award also supports participation of women and underrepresented groups in engineering research and outreach efforts by the investigators with middle and high school students.The objective of this research is to formulate relationships between an applied electric field during the extrusion of thermoplastic ionomer/piezoelectric composite and its resulting material properties (e.g., optical clarity, strength, piezoelectric strain coefficient, and interfacial adhesion between polymer matrix and nanoparticles). In a thermoplastic ionomer, the difference in polarity between the hydrocarbon chain and ionic group creates an electrostatic driving force and results in aggregation of ions. In this context, there exists a knowledge gap on the aggregation of ions in a thermoplastic ionomer above its melting temperature under the influence of an externally applied electric field. In order to understand how an electric field (greater than the electrostatic force of aggregation) applied to a mixture of thermoplastic ionomer/piezoelectric additive affects aggregation morphology (size, distribution in the matrix and around nanoscale additives), the research team will conduct experimental research and coarse-grained molecular dynamics simulations of a representative thermoplastic ionomer with piezoelectric additives (ethylene/methacrylic acid with PZT-5H and PVDF).