Counting All Photons: Efficient Optimization of Visible Light 3D Printing

Abstract

The utility of visible light for 3D printing has increased in recent years owing to its accessibility and reduced materials interactions, such as scattering and absorption/degradation, relative to traditional UV light‐based processes. However, photosystems that react efficiently with visible light often require multiple molecular components and have strong and diverse absorption profiles, increasing the complexity of formulation and printing optimization. Herein, a streamlined method to select and optimize visible light 3D printing conditions is described. First, green light liquid crystal display (LCD) 3D printing using a novel resin is optimized through traditional empirical methods, which involves resin component selection, spectroscopic characterization, time‐intensive 3D printing under several different conditions, and measurements of dimensional accuracy for each printed object. Subsequent analytical quantification of dynamic photon absorption during green light polymerizations unveils relationships to cure depth that enables facile resin and 3D printing optimization using a model that is a modification to the Jacob's equation traditionally used for stereolithographic 3D printing. The approach and model are then validated using a distinct green light‐activated resin for two types of projection‐based 3D printing.

Efficient Near-Infrared Photopolymerizations Using azaBODIPYs with Electron-Donating Groups and Intramolecular Charge Transfer

“…To confirm the effect of halogenation on r p for the best performing derivative, bis­(MeO) 3 -aza X , resins were assessed and compared with those containing (MeO) 3 t Bu-azaBr under conditions employing a constant, low LED intensity of 0.7 mW/cm 2 (Figure D) and wherein the light absorption rate of each PC was equalized (Figure S30). This low-intensity performance test is particularly relevant to emergent LCD-based 3D printing processes where intensities on the order of 1 mW/cm 2 are common . Overall, under constant intensity, k p values of 0.021 ± 0.003, 0.005 ± < 0.001, and 0.102 ± 0.006 M/s were measured for (MeO) 3 t Bu-azaBr, bis­(MeO) 3 -azaH, and bis­(MeO) 3 -azaBr, respectively (Figure D).…”

“…This low-intensity performance test is particularly relevant to emergent LCDbased 3D printing processes where intensities on the order of 1 mW/cm 2 are common. 38 Overall, under constant intensity, k p values of 0.021 ± 0.003, 0.005 ± < 0.001, and 0.102 ± 0.006 M/s were measured for (MeO) 3 tBu-azaBr, bis(MeO) 3 -azaH, and bis(MeO) 3 -azaBr, respectively (Figure 3D). Thus, relative to our previously reported derivative, (MeO) 3 tBu-azBr, the bis(MeO) 3 analogue provided a ∼5× increase in polymerization rate upon exposure to a low-intensity far-red LED, demonstrating higher energy efficiency.…”

3D Printing of Vinylogous Urethane-Based Methacrylic Covalent Adaptable Networks by Vat Photopolymerization

“…This shows that, although Jacob's equation can provide valuable information about the printing conditions, it is necessary to perform an optimization in terms of the overcuring of the sample. Following the optimization protocol defined by Page and co-workers, 31 the Z resolution was optimized by incorporating a small concentration of Sudan I (0.05 wt %), a photo absorbent, to the resin. The incorporation of Sudan I resulted in higher exposure times per layer for the printing (Figure 4a) but a significant improvement on the material overcuring (Figure 4d).…”

Boron-Methylated Dipyrromethene as a Green Light Activated Type I Photoinitiator for Rapid Radical Polymerizations

“…Monomer to polymer conversion was determined by monitoring the peak at ∼770 cm –1 (CC vinylic stretch) during LED irradiation. Initial experiments were performed with 0.3 mol % BODIPY and a green LED intensity of 4 mW/cm 2 , which are conditions relevant to contemporary projection-based 3D printing (e.g., digital light processing and liquid crystal display). Fully formed resins were purged with an inert gas (e.g., argon) to remove oxygen as a potential radical and triplet excited state scavenger.…”