Taming heat in
volumetric printing
with RAFT

Controlling reaction heat in volumetric printing with RAFT polymerization

Computed axial lithography forms a whole object at once, so the entire printed volume polymerizes almost simultaneously. With conventional free-radical photopolymerization that is strongly exothermic: the resin can warm by more than 60 °C, triggering auto-acceleration and thermally driven buoyant flow that move the part while it is still soft. Heat release, not optics, then limits fidelity and part size.

In a collaboration with Derek Irvine’s and Ricky Wildman’s groups at the University of Nottingham, we introduced reversible addition–fragmentation chain-transfer (RAFT) polymerization into CAL. By regulating chain growth, RAFT keeps the reaction kinetics steady and suppresses the abrupt viscosity rise of free-radical systems. In-situ thermal monitoring showed a substantially smaller temperature rise, thermally induced buoyancy was suppressed, and geometries that fail with free-radical resins became printable in several (meth)acrylate systems. Because the RAFT end-groups remain active, printed parts can also be chemically functionalized after printing.

The work reframes volumetric printing as a coupled problem in reaction kinetics, heat transport and the mechanics of a gelling solid, and points toward larger, thermally stable volumetric prints.

Three spheres printed with free-radical and with RAFT-mediated resin
Fig. 1: Three spheres (10, 5 and 2.5 mm in diameter) designed with 150 µm (three-pixel) gaps between them. (A) With conventional free-radical polymerization, the largest sphere heats, rises while still soft and fuses with the others. (B) With RAFT polymerization the spheres form in place and remain separate. Scale bars: 1 mm. From Krumins et al., Nature Communications 17, 6907 (2026), Fig. 3, under a CC BY 4.0 license.
Five test geometries printed with RAFT-mediated resins in three polymer systems
Fig. 2: Five test geometries (Thinker, U-channel, hollow tube, cone and hollow cube) printed with RAFT-mediated resins in three polymer systems. Scale bars: 1 mm. From Krumins et al. (2026), Fig. 4, CC BY 4.0.

Banner: infrared thermal images of the print vial. With conventional free-radical resin the peak temperature reaches 49.7 °C after one minute and 70.1 °C after three (left and center); with RAFT it stays at 34.2 °C (right). From Krumins et al. (2026), Fig. 2, CC BY 4.0.

Key publications

[J65] E. Krumins, Y. Sun, L. Jiang, V. Taresco, D.J. Keddie, R.D. Wildman, H. Taylor, and D.J. Irvine, “Enhanced volumetric additive manufacturing via reversible addition–fragmentation chain transfer (RAFT) polymerization,” Nature Communications, vol. 17, 6907, 2026. doi:10.1038/s41467-026-73456-8