Dynamic Collector Speed in Melt Electrowriting: Enhancing Scaffold Symmetry and 4D Printing Characteristics in Spindle-like Constructs

Melt Electrowriting (MEW) enables the fabrication of microscale fibrous scaffolds through controlled melt extrusion under an electric field. The quality of the printed structures is sensitive to several parameters, including voltage, printing pressure, melt temperature, nozzle-to-substrate gap, and collector speed. Within this parameter set, collector speed has a dominant effect on fiber path control, fiber diameter consistency, deposition accuracy, and the final scaffold architecture. In this study, the use of dynamic collector speed (DCS) whereby the collector speed is varied during printing, is introduced as a means to enhance structural precision. Multiple DCS patterns, including linear, stepwise, and alternating-speed modes, were implemented and compared to constant speed controls to assess their impact on scaffold fidelity. This study focuses on spindle-shaped scaffolds, selected for their anisotropic geometry, which makes them a suitable model for structures requiring directional mechanical properties such as muscle tissue. Results show that employing DCS significantly improves the symmetry of spindle scaffolds, particularly in the vertical (side view) direction, where gravitational effects at low speeds often cause deviation. In addition to improving geometric fidelity, DCS also amplified the spindles' 4D printing performance, increasing their electro-responsive shape change. Overall, our findings demonstrate that DCS is a versatile and easily implementable parameter for improving MEW scaffold fidelity and enabling more complex, high-precision architectures.