Optimization of a High Internal Phase Emulsion-Based Resin for Use in Commercial Vat Photopolymerization Additive Manufacturing

Abstract

High internal phase emulsions (HIPEs) are potential stereolithography-based resins for producing innovative lightweight porous materials; however, the use of these resins has only been shown in bespoke stereolithography setups. These studies indicated that HIPEs tend to scatter the light during structuring via stereolithography, and can produce poorly defined, and low-resolution structures, but the inclusion of light absorbers can drastically increase the printing resolution. In this study, we focused on the inclusion of biocompatible light absorbers within the resin and the compatibility of those resins with a commercial vat photopolymerization additive manufacturing (or stereolithography) setup. A surfactant (hypermer) stabilized water-in-oil emulsion based on 2-ethylhexyl-acrylate and isobornylacrylate was used. For the light absorbers, both hydrophobic (beta-carotene) and hydrophilic (tartrazine) molecules were used, which dissolve in the organic phase and aqueous phase, respectively. It was found that using a combination of both beta-carotene and tartrazine provided the best stereolithography-based 3D printing resolution. Additionally, the emulsion was stable for the duration of the printing process and showed a porous polyHIPE structure with open surface porosity. The formulation of these HIPE-based resins permits them to be used in a wide range of applications since complex structures could be fabricated from HIPEs.

Investigating the Potential of Electroless Nickel Plating for Fabricating Ultra-Porous Metal-Based Lattice Structures Using PolyHIPE Templates

“…The surfactant was dissolved in the mixture by heating it until it was completely dissolved at 50 °C. β-Carotene and tartrazine that were optimized in our previous work were added at 0.02 and 0.06 wt % with respect to the continuous organic phase, respectively, to act as light absorbers . The photoinitiator was then added to the continuous phase at 5 wt %.…”

“…β-Carotene and tartrazine that were optimized in our previous work were added at 0.02 and 0.06 wt % with respect to the continuous organic phase, respectively, to act as light absorbers. 32 The photoinitiator was then added to the continuous phase at 5 wt %. Finally, 80 vol % distilled water, dH 2 O, as the internal phase was added dropwise while stirring the mixture at 300 rpm to form an emulsion using a SciQuip-Pro 40 stirrer.…”

“…Traditional manufacturing methods of polyHIPEs such as casting (molding) can only produce geometrically simple designs and do not offer flexibility in the production of the polyHIPEs. , On the other hand, inherently porous and intricate lightweight structures including lattice structures can be fabricated via the combination of emulsion templating with additive manufacturing within a single step. ,,, Among additive manufacturing (AM) techniques, stereolithography (SLA-vat photopolymerization) has the advantage of fabricating the 3D intricate structures directly from the design file with minimum effort. In this AM technique, commercial photocurable resins or emulsion-based resins are used as 3D printing materials. ,,− …”

“…To produce metal lattices, normally, nonporous polymer templates are used. Recently, we developed a polymer resin that inherently porous via using emulsion templating and we reported its use as a resin for vat photopolymerization. , In particular, polymerized high internal phase emulsions (polyHIPEs), porous polymers produced by a straightforward emulsion templating process, were used . In this process, two immiscible liquids (in our case a hydrophobic methacrylate phase and water) are mixed stabilized by surfactants or colloidal particles to form a continuous (external) phase and internal (droplet) phase.…”

“…In this AM technique, commercial photocurable resins or emulsion-based resins are used as 3D printing materials. 32 , 33 , 48 − 53 …”