Frontal Conversion and Uniformity in 3D Printing by Photopolymerisation

Area of Science:

• Polymer Science
• Materials Science
• Additive Manufacturing

Background:

• Photopolymerization in 3D printing exhibits non-uniform spatio-temporal conversion.
• This intrinsic characteristic can lead to detrimental effects like differential shrinkage and material property inhomogeneity.

Purpose of the Study:

• To investigate the impact of non-uniform photopolymerization kinetics on light-driven 3D printing.
• To develop a framework for optimizing 3D printing processes and designing complex materials by controlling polymerization and stage displacement.

Main Methods:

• Experimental investigation of acrylate and thiol-ene systems (neat and dye-doped).
• Analysis using a coarse-grained photopolymerization model.
• Quantification of monomer-to-polymer conversion via patterning, FT-IR mapping, and modeling.

Main Results:

• Characterized sigmoidal monomer-to-polymer conversion profiles.
• Identified regimes where polymerization conversion (z) is smaller than, commensurate with, or larger than stage displacement (Δz).
• Demonstrated opportunities for fabricating materials with controlled modulation along the illumination axis.

Conclusions:

• Non-monotonic conversion, while potentially detrimental, can be leveraged for material design.
• A simple framework coupling stage displacement and polymerization kinetics aids process optimization.
• Enables precise design of complex, internally stratified materials in photopolymerization-based 3D printing.