Recent Trends in Stereolithography Resin Formulation and Photoinitiator Systems with Sustainability Perspectives

Stereolithography (SLA) is a high-resolution additive manufacturing technique that fabricates complex structures through light induced photopolymerization of liquid resin systems. This review evaluates recent developments in SLA resin formulations, photoinitiator systems, and sustainability considerations that influence printing performance and environmental impact. Literature was sourced from Google Scholar, ScienceDirect, IEEE Xplore, Scopus, and Web of Science using keywords such as "Stereolithography" and "additive manufacturing," prioritizing studies from the past decade and following PRISMA guidelines. Previous studies report several classes of photocurable resins used in SLA, including acrylate and methacrylate resins, epoxy acrylates, urethane acrylates, poly(methyl methacrylate) systems, and emerging biobased resins derived from soybean oil, polycaprolactone, vanillin, and chitosan derivatives. These materials have been investigated for applications such as dental devices, tissue engineering scaffolds, conductive components, and reinforced composite structures. Photopolymerization efficiency in SLA is strongly governed by photoinitiators that generate reactive radicals upon light irradiation. Representative examples include Type I photoinitiators such as trimethylbenzoyl diphenylphosphine oxide and hydroxyacetophenone derivatives, and Type II photoinitiators such as benzophenone, camphorquinone, eosin Y, riboflavin, and curcumin. Recent research has also examined natural photoinitiators including chlorophyll, chalcones, coumarins, and naphthoquinone derivatives as alternatives to petroleum derived systems. This review critically examines recent SLA resin formulations and photoinitiator systems, emphasizing naturally derived photoinitiators and their effects on curing efficiency, material properties, and environmental performance. Applications across medical and non-medical sectors are evaluated to contextualize material requirements, while life cycle considerations highlight trade-offs between conventional petroleum-based and emerging bio-based resins, particularly in developing regions. Analysis indicates a growing focus on sustainable monomers, functional additives, and visible-light photoinitiators, though challenges in cost, recyclability, and long-term stability remain for broader SLA adoption.