Laser supports Direct Ink Writing: Thermoset 3D printing as a free-standing structure

Thermoset polymers are difficult to process in 3D printing because, once cured, they can no longer be remelted, and crosslinking must be controlled precisely during extrusion. In Direct Ink Writing (DIW), shape stability is therefore often enhanced by thermal, acoustic, or UV-assisted fields. According to the authors, however, this still leaves problems with curing speed, material compatibility, and the reproducible tuning of properties. For complex, free-standing geometries, support materials are also frequently printed and later removed.

A team led by Professor Wu Dezhi at the Pen-Tung Sah Institute of Micro-Nano Science and Technology of Xiamen University presents, in the paper “Laser-assisted direct three-dimensional printing of free-standing thermoset devices,” a DIW variant that integrates curing directly into the writing motion. While the nozzle deposits a microscale polymer jet, a focused laser irradiates the jet immediately after it exits. Through the photothermal effect, crosslinking is triggered in situ; according to the study, solidification is achieved in less than 0.25 seconds.

The rapid build-up of strength is intended to enable free-standing thermoset structures without support material, even for complex 3D architectures. The team reports a structural resolution of 50 micrometers. At the same time, the crosslink density can be controlled via laser power, exposure time, and writing speed. This allows the mechanical properties, according to the authors, to be varied by up to a factor of ten, and electrical properties by up to a factor of twenty.

As applications, the researchers cite flexible electronics, microfluidics, and soft robotics, where fine channels, stiffness gradients, and functional integration in a single print run are required. Organ-on-chip setups and biomedical scaffolds could also benefit if the method can be transferred to additional resin systems and stably controlled for larger components. In practice, it will also matter how laser optics and temperature management can be integrated into existing DIW platforms, and how robust the process remains in continuous operation.