Multi-Material Light-Based Additive Manufacturing of Chromophore Containing Materials

Polymers are essential materials for modern technologies, and additive manufacturing (AM) approaches are required to fabricate complex structures with tailored properties for emerging applications. Light-based 3D printing techniques, such as digital light processing (DLP) and two-photon laser printing (2PLP), offer high fabrication precision for complex structures with excellent surface finishes. Depending on the intended application, each technique offers distinct advantages and is therefore selectively applied across the four studies. Optical applications demand outstanding resolution, rendering 2PLP the method of choice to investigate incorporation of red, green, and blue (RGB) fluorescent molecules into ink formulations for the fabrication of emissive microstructures with covalently incorporated emitters. After optimizing the printing and emission properties of the microstructures, complex RGB emissive multi-material specimens are printed, highlighting potential applications in anticounterfeiting devices and displays. To 3D print structures in the centimeter regime where resolutions in the tens of micrometers are sufficient, DLP printing is the method of choice. Therefore, an ink formulation enabling multi-material single-vat dual-wavelength 4D DLP printing is developed. Orthogonal photochemistry enables selective printing of shape memory polymers (SMPs) under blue-light irradiation, while ultraviolet (UV)-light induces the polymerization of the SMP as well as the static epoxy-based material, thereby suppressing the shape memory effect. The desired material properties are achieved through washing and thermal post-treatment. Finally, the fabrication of multi-material structures with locally controlled material properties is demonstrated from a single-vat by only using different wavelengths of light for printing. DLP printing is also suitable for the fabrication of mechanochromic materials, which respond to mechanical force with a pronounced color change. This is demonstrated by DLP printing a spiropyran (Sp)-containing tube specimen, which upon compression turns from yellow to purple. Irradiation with visible (Vis)-light recovers the initial color and shape. A dog bone shaped specimen is used to demonstrate the response to tensile stress. The straightforward synthesis of Sp and commercial availability of all other components indicates strong potential for scalability and real-time visual force sensing applications. Combining the two previous macro-scale projects, single-vat dual-wavelength DLP printing is applied, to fabricate colorless structures (405 nm LED) and program information into them by locally controlled initiating the isomerization of the photochromic Sp to the colorful merocyanine (Mc) (365 nm LED). The exposure to the orthogonal stimuli pH and heat enable the reversible encryption or permanent deletion of the information on demand. This system can be applied in advanced information storage and sensing applications. This thesis demonstrates how light-based AM techniques can be applied to 3D print chromophore containing multi-material structures on the application relevant scale.