Scattering Model for Composite Stereolithography to Enable Resin–Filler Selection and Cure Depth Control

Abstract

Fillers are used to modify the properties of the photoresins used in stereolithography (SLA). The resulting composite formulations tend to have a decreasing cure depth for increasing particle loadings due to light scattering. However, some composites, such as those loaded with silica or polymethyl methacrylate particles, show the opposite effect: the cure depth increases with the particle loading. To unify these seemingly contradictory observations, we propose a modified Lambert–Beer equation. Depending on the filler properties, we differentiate between three scenarios: (i) scattering-dominated, (ii) weakly scattering, and (iii) nonscattering (refractive index-matched). In the first case, the cure depth of the resin decreased with an increasing solid loading, whereas in the other cases, the opposite trend was observed. These findings have significant implications for the formulation of composite SLA resins in terms of materials selection and printing parameter optimization.

Photocurable resin-silica composites with low thermal expansion for 3D printing microfluidic components onto printed circuit boards

“…Apart from their advantages with respect to their CTE and Young's modulus values, the combination of silica and an Esun resin has another benefit compared to other filler/resin formulations. As SLA is a light-based technique, strong light scattering by the ceramic filler should be avoided by selecting refractive index-matching materials [56]. For this reason, a formulation of silica with Esun resin is better suited than alumina-Esun resin, silica-Formlabs resin, or alumina-Formlabs resin formulations [56].…”

“…As SLA is a light-based technique, strong light scattering by the ceramic filler should be avoided by selecting refractive index-matching materials [56]. For this reason, a formulation of silica with Esun resin is better suited than alumina-Esun resin, silica-Formlabs resin, or alumina-Formlabs resin formulations [56]. The silica powder (SS1402, Industrial Powder, USA) has a density of ~2.2 g/cm 3 and a size of 2 µm (d 50 ); its shape and particle size distribution (PSD) can be found in Figs.…”

“…Here, Φ p represents the theoretical maximum packing fraction for information regarding our cure depth experiments can be found in our previous research [56].…”

Filling Aggregation-Induced Extinction Mechanism in Near-Infrared Photopolymerization for Gradient and Highly Filled Bulk Materials

“…However, composite fillers often absorb, refract, or scatter incident light, leading to the increase in the lightattenuation gradient. 17,18 Such extinction behaviors, especially in the case of a high filler content, intensively weaken the light penetration through the entire polymerizable medium and inhibits photopolymerization; these eventually lead to the deterioration of material performances, and therefore photopolymerization of highly filled systems remains a profound challenge. 19 In parallel, numerous studies have reported a growing interest in composites photopolymerization with a high filler content, including fabrication of high-performance or functional materials.…”

“…Photopolymers integrated with rich functional fillers may render fresh performance to the polymers, spanning from high mechanical properties and dielectric properties, refractive index, and electrical conductivity as well as multiple stimuli responsiveness. − The functionalities of photopolymers are significantly improved with the increase of filler content. However, composite fillers often absorb, refract, or scatter incident light, leading to the increase in the light-attenuation gradient. , Such extinction behaviors, especially in the case of a high filler content, intensively weaken the light penetration through the entire polymerizable medium and inhibits photopolymerization; these eventually lead to the deterioration of material performances, and therefore photopolymerization of highly filled systems remains a profound challenge . In parallel, numerous studies have reported a growing interest in composites photopolymerization with a high filler content, including fabrication of high-performance or functional materials. ,− …”