Printability of Poly(lactic acid) Ink by Embedded 3D Printing via Immersion Precipitation.

Area of Science:

• Materials Science
• Chemical Engineering
• Additive Manufacturing

Background:

• Immersion precipitation 3D printing (ip3DP) and freeform polymer precipitation (FPP) are advanced techniques for fabricating 3D structures via nonsolvent-induced phase separation using direct ink writing (DIW).
• Understanding the complex interplay of solvents, nonsolvents, and polymers is crucial for optimizing the printability and structural integrity of 3D printed objects using these methods.

Purpose of the Study:

• To characterize ip3DP and FPP methods for fabricating 3D structures using polylactide (PLA) in dichloromethane as a model system.
• To analyze the rheological properties of PLA inks and the impact of printing parameters on solvent-nonsolvent diffusion to achieve successful 3D printing.
• To establish guidelines and a processing map for the fabrication of complex 3D structures with tailored porosity.

Main Methods:

• Characterization of polylactide (PLA) solutions in dichloromethane (7.5-30% w/w) as model inks for 3D printing.
• Analysis of rheological properties, including shear-thinning behavior and viscosity variations.
• Investigation of the effect of printing parameters (ink concentration, nozzle diameter, applied pressure, nozzle speed) on solvent-nonsolvent diffusion and printability.
• Development of a processing map to identify optimal printing conditions.
• Demonstration of porosity control by adjusting PLA concentration and porogen addition.

Main Results:

• PLA inks exhibited shear-thinning properties with viscosities spanning three orders of magnitude (10⁻¹ to 10² Pa·s).
• A processing map was developed, defining ideal ranges for PLA concentration and nozzle diameter to ensure printability.
• Complex 3D structures were successfully fabricated by controlling applied pressure and nozzle speed, showcasing advantages over solvent evaporation methods.
• The porosity of printed objects, both at the interface and internally, was effectively tailored by ink composition and porogen inclusion.

Conclusions:

• Immersion precipitation and freeform polymer precipitation offer versatile platforms for 3D printing thermoplastics with tunable nanometer-scale porosity.
• The developed processing map and understanding of parameter effects provide essential guidelines for successful embedded 3D printing using these phase-separation techniques.
• These methods enable the fabrication of micro-to-centimeter scale objects with precise control over structural and pore characteristics.