Preparation, characterization and powder-bed laser sintering of biodegradable composite powders

增材制造工艺（如粉末床熔融激光束熔化）对于生产具有个性化形状和性能的复杂部件变得越来越重要。这种工艺在生物医学领域特别有前途，可以生产具有患者特定特性和精确贴合的个性化植入物。该领域的主要当前限制因素是将生物可降解聚合物与功能添加剂组合的合适复合粉末材料的可用性。我们项目的目的是通过开发一个用于生产特定复合粉末的新平台来扩大可用材料的范围。我们的方法使用超粒子作为粉末材料，它可以从定义的初级粒子混合物的受控自组装产生。这些超颗粒为粉末床熔融激光束熔融工艺提供了几个重要的优点：i）通过已建立的方法如基于微乳液的技术，宽范围的聚合物材料作为粉末体系变得可获得; ii）可以通过初级颗粒精确地调节组成并导致组分在最终材料中的均匀分布; iii）由初级颗粒的尺寸产生限定的和可调节的表面粗糙度，并促进流动性，从而促进均匀和致密的粉末床。我们将证明这个过程的优点，生物医学相关的材料系统组成的生物可降解的聚乳酸聚合物与功能添加剂。这些新的粉末系统的有效加工和粉末设计中不同自由度的实现需要开发材料有效的印刷工艺。这需要开发一种用于处理少量粉末的台式激光束熔化系统。此外，激光束源和粉末颗粒结构之间的相互作用对所得到的部件性能起着关键作用。作为标准，CO2激光器（10.6 µm）用于热塑性塑料的激光束熔化，因为聚合物有效地吸收红外线。然而，这会导致高热量输入，因此存在热不稳定生物聚合物（如PLA和添加的治疗分子）降解的风险。因此，该项目的目标是将激光源改为二极管激光系统（445 nm），从而能够通过嵌入的吸收纳米颗粒直接实现激光辐射的体积耦合，从而需要更少的能量引入粉末中。该项目的总体目标是建立基本的工艺-结构-性能关系，从而通过超微粒粉末的结构、形态和组成优化粉末床熔融工艺和所得性能。

Additive manufacturing processes such as powder bed-fusion laser beam melting are becoming increasingly important for the production of complex components with individualized shapes and properties. Such processes are especially promising in the biomedical sector to produce personalized implants with patient-specific properties and exact fit. A major current limiting factor in this field is the availability of suitable composite powder materials that combine biodegradable polymers with functional additives. The aim of our project is to expand the available range of materials for by developing a new platform for the production of defined composite powders. Our approach uses supraparticles as powder materials, which can be produced from the controlled self-assembly of defined primary particle mixtures. These supraparticles offer several important advantages for the powder bed fusion laser beam melting process: i) a wide range of polymeric materials becomes accessible as powder systems by established methods such as miniemulsion-based techniques; ii) the composition can be precisely adjusted via the primary particles and leads to homogeneous distributions of the components in the final material; iii) a defined and adjustable surface roughness results from the size of the primary particles and promotes flowability and thus a homogeneous and dense powder bed. We will demonstrate the advantages of this process for a biomedically relevant material system consisting of biodegradable polyactide polymers with functional additives. An effective processing of these new powder systems and the realization of the different degrees of freedom in the powder design requires the development of a materials-effective printing process. This requires the development of a desktop laser beam melting system for processing small powder quantities. Furthermore, the interaction between the laser beam source and the structure of the powder particles plays a key role for the resulting component properties. As a standard, CO2 lasers (10.6 µm) are used for laser beam melting of thermoplastics, since polymers effectively absorb in the IR. However, this leads to a high heat input and therefore risks the degradation of thermolabile biopolymers such as PLA and added therapeutic molecules. Therefore, the project aims at changing the laser source to a diode laser system (445nm), which enables the volume-like coupling of the laser radiation directly via embedded, absorbing nanoparticles and thus requires less energy to be introduced into the powder. The overall goal of the project is to establish fundamental process-structure-property relationships that will enable the optimization of the powder bed fusion process and the resulting properties via the structure, morphology and composition of the supraparticle powders.