Additive Manufacturing of Controlled Anisotropic Materials via Electrically Assisted Nanocomposite Fabrication

增材制造（AM）已经成为一种有前途的快速制造方法，适用于各种行业。目前的增材制造工艺可以很好地控制模型的形状，但不能控制其材料性能。大多数增材制造工艺只能制造具有各向同性材料特性的结构（它们在所有方向上都是相同的）。该奖项支持一种新型增材制造工艺的基础研究，该工艺可以准确地创造各向异性材料特性（随方向变化的特性）。这是在三维（3D）结构中完成的，通过在制造每层时动态控制电场，从而使短纤维增强物（以碳纳米管或金属薄片的形式）在聚合物中定向。形状是通过改变每一层的投影图像来实现的。因此，即使使用单一类型的纳米复合材料，也可以在制造结构中实现不同的材料性能。研究结果将显著扩展增材制造工艺制造具有增强结构、热学和电学性能的各向异性材料的能力。这种能力将使抗冲击纳米复合材料、热超材料和可穿戴传感器的新设计和制造成为可能。新的制造工艺将为美国公司提供竞争优势，并可能导致航空航天、消费电子、国防和医疗行业的创新。研究成果将整合到本科/研究生课程开发中，以及增加少数民族参与的外展项目中。研究目标是建立一种基于电辅助掩模图像投影的立体光刻（eMIP-SL）工艺，该工艺可以使用控制碳纳米管（CNT）对齐的纳米复合材料来构建三维形状，以增强功能特征。将进行电极设计、纳米复合材料制备、碳纳米管对准控制和基于投影的立体光刻集成等任务。研究了碳纳米管排列结构的各向异性力学/电/热性能的基本特征，包括测量各向异性力学性能、电导率和热传导率，以及光学/扫描电子显微镜下的微观结构观察。将研究各向异性机械/电/热性能的基本机制，作为工艺参数和产生的纳米/微结构的函数。该研究成果将为eMIP-SL工艺提供科学和工程知识，以利用纳米复合材料的可控性能制造各向异性多功能3D结构。

Additive manufacturing (AM) has emerged as a promising rapid manufacturing approach for a wide variety of industries. Current AM processes can fabricate a model with good control on its shape but not on its material properties. Most AM processes only enable the fabrication of structures with isotropic material properties (they are the same in all directions). This award supports fundamental research on a novel additive manufacturing process that can accurately create anisotropic material properties (properties that vary with direction). This is accomplished in a three-dimensional (3D) structure by dynamically controlling electric fields while fabricating each layer, which has the result of orienting the short fiber reinforcement (in the form of carbon nanotubes or metal flakes) in the polymer. The shape is achieved by changing the projection image for each layer. Hence, varying material properties can be achieved in the fabricated structure even when using a single type of nanocomposite. The research results will significantly expand the capability of AM processes to fabricate anisotropic materials with enhanced structural, thermal, and electric properties. Such capability will enable novel design and fabrication of impact resistant nanocomposites, thermo-metamaterials, and wearable sensors. The new manufacturing process will provide US companies with a competitive edge and can lead to innovations in aerospace, consumer electronics, defense, and medical industries. The research outcomes will be integrated into undergraduate/graduate course development, as well as outreach programs to increase minority participation.The research objective is to establish an electrically assisted mask-image-projection-based stereolithography (eMIP-SL) process that can build three-dimensional shapes using nanocomposites with controlled carbon nanotube (CNT) alignment for enhanced functional characteristics. Tasks on electrode design, nanocomposite preparation, CNT alignment control, and integration with projection-based stereolithography will be performed. The fundamental characteristic of the anisotropic mechanical/electrical/thermal properties of architectures with aligned carbon nanotubes will be studied including measuring the anisotropic mechanical properties, the electrical and thermal conductivities, and microstructure observation with optical/scanning electron microscopy. The fundamental mechanism for the anisotropic mechanical/electrical/thermal properties in the fabricated architectures will be studied as a function of the process parameters and resulting nano/microstructures. The research result will develop scientific and engineering knowledge on the eMIP-SL process for fabricating anisotropic multi-functional 3D structures using controlled properties of nanocomposites.