Enhanced volumetric additive manufacturing via Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization

Abstract

Computed Axial Lithography (CAL), a Volumetric Additive Manufacturing (VAM) technology, enables the rapid, full body i.e. not layer-by-layer, fabrication of freeform geometries within seconds through the superposition of projected light patterns. However, as conventional CAL relies on free radical polymerization (FRP), it is an intrinsically exothermic process (ΔT > 60 °C) that can trigger auto-acceleration, so compromising print fidelity and limiting scalability. By regulating polymer chain length during propagation through reversible chain transfer, Reversible Addition–Fragmentation Chain Transfer (RAFT) maintains steady, controlled reaction kinetics and prevents the sharp viscosity increase characteristic of FRP. In this study, we introduce RAFT polymerization into various (meth)acrylate-based systems within CAL to effectively mitigate heat generation and suppress auto-acceleration during photopolymerization. The success of this approach is confirmed by in-situ thermal monitoring and the suppression of thermally induced buoyancy, revealing a substantial reduction in temperature rise compared to FRP. Furthermore, RAFT chemistry enables post-printing functionalization of the printed objects, expanding CAL’s chemical versatility. This study demonstrates that RAFT-mediated CAL allows the fabrication of structures inaccessible via FRP, advancing thermally stable and functionally tunable volumetric additive manufacturing.