Multifunctional 3D Printing of Heterogeneous Polymer Structures by Laser-Scanning Micro-Stereolithography Using Reversible Addition–Fragmentation Chain-Transfer Polymerization

Abstract

Stereolithography is the most precise three-dimensional (3D) printing technology and has been applied to various applications with various photocurable materials. However, most 3D-printed objects produced using conventional methods are made of uniform materials, limiting their functions. In this study, to produce heterogeneous 3D-printed objects, microphase-separated structures were controlled by the copolymerization of a photoinduced macro-reversible addition−fragmentation chain-transfer (macro-RAFT) agent and a monomer at different scanning speeds of an ultraviolet laser beam using a laboratory-constructed laserscanning micro-stereolithography system based on a bottom-up configuration in a fully open-to-air system. First, we demonstrated 3D printing using a RAFT agent by fabricating a pyramidal structure using a 375 nm laser. Copolymerization with styrene was performed to confirm that the synthesized poly(butyl acrylate) with dormant species at the end (DTC-PBA) formed block polymers upon photoirradiation. Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) results indicated the formation of a block polymer. A homogeneous photocurable resin was prepared by mixing the synthesized DTC-PBA with multifunctional monomers, and 3D printing was performed using the prepared photocurable resin at different scanning speeds. As the scanning speed increased, the transparency of the 3D-printed model increased, whereas the mechanical strength decreased. It was suggested from scanning probe microscopy (SPM) observations that these differences were due to differences in the microphase-separation structure. As a result, it was demonstrated that heterogeneous 3D structures with sites have different mechanical and optical properties from those of a single material. Controlling the physical properties of 3D-printed parts by controlling the laser irradiation conditions is useful for functionalizing 3D-printed microdevices.

Application of RAFT in 3D Printing: Where Are the Future Opportunities?

“…The field of RAFT-mediated 3D printing has been quickly evolving since first reported. − and its application has been explored in different contexts such as surface functionalization, ,, direct laser writing/surface paterning, self-healing polymers, , polymerization-induced microphase separation, , fabrication of scaffolds with tailored hierarchical porosities, and customized drug delivery systems . The following sections provide a succinct, pertinent introduction and a summary of the reported applications of RAFT-mediated 3D printing in the literature.…”

“…Since it was initially published, − the field of RAFT-mediated 3D printing has rapidly developed and expanded beyond the creation of reprocessable/living 3D materials. ,, This technology has been utilized in cutting-edge applications such as self-healing polymers, surface patterning, nanostructuration, , and customized drug delivery . To accomplish these applications, several chemical mechanisms such as photoiniferter (direct photolysis), , photoinduced electron/energy transfer (PET)-RAFT, , cationic RAFT, , and photoinitiator RAFT , have been utilized.…”

3D Printing of Customized Drug Delivery Systems with Controlled Architecture via Reversible Addition‐Fragmentation Chain Transfer Polymerization

“…[28,47] The scope of RAFT-mediated 3D printing has been progressively evolving, and different photoreaction mechanisms such as photoiniferter, [29,48] photoinduced electron transfer (PET)-RAFT, [30,36] and cationic RAFT [35,49] have been investigated. Applications of RAFT-based 3D printing in self-healing polymers, [31,50] direct laser writing/surface patterning, [33] surface functionalization, [30,32,48] and polymerization-induced microphase separation [51,52] have been reported. Recently our group reported on RAFT-mediated 3D printing of scaffolds with tailored hierarchical porosities and highly resolved micro-and macroscale features.…”

3D printing soluble solids via PISA

“…6 Bagheri et al, Zhao et al, and Maruyama et al also similarly explored RAFTbased photopolymerization for DLP printing. [7][8][9] Boyer et al further extended photopolymerization techniques involving RAFT to multi-functional RAFT agents, illustrating how RAFT agent functionality can be adjusted to fine-tune mechanical properties and glass transition temperature. 10 Blais et al investigated PISA for producing "loop-stabilized" particles using a difunctional poly(DMA) macro-CTA while Gao et al polymerized styrene from monofunctional and difunctional PEG-based macro-CTAs (chain transfer agents) to form AB diblock and BAB triblock copolymers.…”