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

粉末床熔合激光束熔化等增材制造工艺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。这种方法在生物医学领域尤其有前途，可以生产具有患者特定特性和精确匹配的个性化植入物。该领域的一个主要限制因素是合适的复合粉末材料的可用性，这种材料将可生物降解聚合物与功能添加剂结合在一起。我们项目的目的是通过开发一个新的平台来生产确定的复合粉末，以扩大材料的可用范围。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中产生。这些超粒子为粉末床熔融激光束熔化工艺提供了几个重要的优势：i)通过现有的方法，如微乳化技术，广泛的聚合物材料可以作为粉末系统获得；Ii)成分可以通过初级颗粒精确调整，并导致最终材料中成分的均匀分布；Iii)一个确定的和可调节的表面粗糙度的结果，从主要颗粒的大小，促进流动性，从而一个均匀和致密的粉末床。我们将展示该工艺在生物医学相关材料体系中的优势，该体系由可生物降解的聚乳酸聚合物和功能添加剂组成。要有效地处理这些新型粉末系统并实现粉末设计中的不同自由度，就需要开发一种材料有效的印刷工艺。这就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，激光束源与粉末颗粒结构之间的相互作用对所得组件的性能起着关键作用。作为标准，CO2激光器（10.6µm）用于热塑性塑料的激光束熔化，因为聚合物可以有效地吸收红外。然而，这会导致高热量输入，因此有降解耐热性生物聚合物（如PLA）和添加治疗分子的风险。因此，该项目旨在将激光源改为二极管激光系统（445nm），该系统可以直接通过嵌入吸收纳米颗粒实现激光辐射的体状耦合，从而减少向粉末中引入的能量。该项目的总体目标是建立基本的工艺-结构-性能关系，从而通过超颗粒粉末的结构、形态和组成来优化粉末床熔合工艺和最终性能。

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.