Filament Disturbance and Fusion during Embedded 3D Printing of Silicones

Area of Science:

• Materials Science
• Additive Manufacturing
• Fluid Dynamics

Background:

• Embedded 3D printing (EMB3D) fabricates soft materials using a yield stress fluid support bath.
• Lack of filament fusion is a key defect in EMB3D due to support fluid displacement.
• Interfacial tension has been explored to enhance fusion but can also cause filament rupture.

Purpose of the Study:

• To evaluate the role of interfacial tension in controlling defects during embedded 3D printing.
• To investigate the impact of support rheology, interfacial tension, print speed, and spacing on filament fusion and defects.
• To understand the interplay between capillary instabilities and material properties in EMB3D.

Main Methods:

• Utilized polydimethylsiloxane (PDMS)-based inks with varying silica and surfactant content.
• Printed parallel filaments into Laponite-in-water support baths.
• Employed digital image analysis to quantify filament shrinkage, rupture, fusion, and positioning defects.

Main Results:

• Capillary instabilities and interfilament fusion are governed by the balance between support rheology and interfacial tension.
• Lower support viscosity and higher interfacial tension increase filament shrinkage and rupture.
• Achieving interfilament fusion necessitates material overextrusion, particularly in high-viscosity supports and low interfacial tension conditions.
• Printing orientation significantly impacts fusion quality and filament displacement.

Conclusions:

• Optimizing embedded 3D printing requires careful management of interfacial tension and support rheology.
• Material overextrusion is essential for robust interfilament fusion.
• Specialized slicing algorithms are needed to account for orientation-dependent spacing and achieve precise control in EMB3D.