Hot – 2PP: Development of a heating device and testing of materials for high temperature two-photon polymerization – 3D printing

Abstract

Additive manufacturing – commonly called 3D printing – is a rapidly evolving field of research and industry that allows the automated production of complex workpieces from digital three-dimensional geometries. Two-photon polymerization (2PP) is an additive manufacturing process that enables the production of highly detailed functional parts with sub-micrometer resolution. Significant increases in production speed within recent years make two-photon-polymerization viable for industrial applications, due to its high resolution, especially for biomedical e.g. microfluidics for dynamic cell culture applications or scaffolds for tissue engineering in regenerative medicine. This results in a growing demand for novel, biocompatible materials suitable for two-photon 3D printing. The aim of this thesis was to develop and test an apparatus for heating small amounts of printing resin, to test materials for high temperature 2PP. The focus of the design was on modularity and adaptability, allowing fast testing of multiple material samples in a short time. The sample heating system consists of a steel and glass sample holding chamber with a magnetically attached heating element. Heating was provided by two resistive metal ceramic heaters, regulated by a PID controller. Temperature feedback was provided by a thermocouple and the heating device was calibrated by referencing the testing five different experimental materials - each with several composition variants - by conducting polymerization threshold tests, with varying processing temperatures and print settings. The test structures were arrays of cubes as well as spherical scaffolds, called buckyballs.The experiments served as a proof-of-concept for high temperature 2PP, however several adverse effects of increased processing temperature were identified, which must be addressed to obtain viable 2PP materials.