Multi-Material Ink Direct Writing System with Material Switching Optimization

Multi-material direct ink writing (M-DIW) is an advanced additive manufacturing technology capable of fabricating complex soft polymeric structures. However, material switching during M-DIW presents challenges such as switching lag and coextrusion, which significantly affect printing accuracy and fidelity. To address these issues, this study develops an M-DIW system integrating a pneumatic extrusion control system and a multichannel printhead, enabling material switching during printing. To enhance printing performance, a flow rate-pressure model is established to analyze ink extrusion dynamics, and a static ink pre-extrusion control strategy is proposed to minimize switching lag while mitigating coextrusion effects. Experimental validation demonstrates that the proposed method effectively improves material switching precision, ensuring high-resolution multi-material printing. Multiple printing case studies, including checkerboard patterns and functional soft structures, confirm that the system can achieve rapid material switching during printing while ensuring sharp material boundaries. This research provides an optimized method for M-DIW printing, broadening the scope of complex soft structures that can be designed and manufactured.