Delayed Crosslinking Enables Ultra-High-Resolution Melt Electrowriting of Responsive Liquid Crystal Elastomers

Abstract

Melt electrowriting (MEW) enables the fabrication of finely structured scaffolds with sub-micrometer resolution. However, reducing the inter-fiber distance (IFD) in MEW remains challenging due to electrostatic interactions between the charged polymer jet and previously deposited fibers, often leading to fiber bridging. Recently, we demonstrated that MEW of reactive liquid crystalline inks, followed by ultraviolet (UV) photopolymerization, enables the fabrication of digitally positioned liquid crystal elastomer (LCE) structures. Building on this, we demonstrate that tuning the UV light intensity during photopolymerization significantly improves the achievable resolution range. Lower UV intensities produce smaller minimum IFDs without fiber bridging, enabling the fabrication of highly ordered structures with IFDs down to 11 µm for 5 µm-diameter fibers, a feature that, to the best of our knowledge, surpasses the smallest IFDs previously reported for MEW. We hypothesize that slower crosslinking kinetics extend the time window for charge dissipation, reducing electrostatic interactions between the jet and the previously deposited fibers. Although the mechanism remains unclear, local variations in material flow or curing-induced surface morphology may also affect electric field distribution. Beyond resolution improvements, this strategy enables defect-free fabrication of stimuli-responsive LCEs with programmable shape transformation and actuation. UV light intensity thus emerges as a critical design parameter for MEW, with implications for other photo-crosslinkable systems.