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.