Controlling Morphing Behavior in 4D Printing: A Review About Microstructure and Macrostructure Changes in Polylactic...

Area of Science:

• Materials Science
• Additive Manufacturing
• Polymer Science

Background:

• Four-dimensional (4D) printing integrates stimulus-responsive materials with additive manufacturing (AM) to produce 3D objects capable of programmed shape changes.
• Controlled morphing remains a key challenge in 4D printing, necessitating a deeper understanding of macroscopic and microscopic behavior.
• This review focuses on thermoplastic poly(lactic acid) (PLA) fabricated via fused deposition modeling (FDM).

Purpose of the Study:

• To investigate the influence of molecular weight, polymer chain modifications, and 3D printing parameters on the shape change capabilities of PLA.
• To establish the relationship between material properties, processing conditions, and the temporal shape transformation of 4D printed structures.
• To identify critical parameters governing the shape memory effect in PLA-based materials.

Main Methods:

• Review of existing literature on 4D printing, focusing on poly(lactic acid) (PLA).
• Analysis of the impact of molecular weight and polymer chain modifications on material properties relevant to shape change.
• Examination of fused deposition modeling (FDM) parameters, including nozzle temperature, fill density, print patterns, and raster angle, and their effect on shape morphing.

Main Results:

• The glass transition temperature (Tg) of PLA is a crucial factor influencing shape change and can be modulated by altering molecular weight.
• 3D printing parameters such as nozzle temperature, fill density, print patterns, and raster angle significantly affect the material's shape change behavior.
• Shape recovery in 4D printed PLA structures is strongly correlated with the chosen recovery temperature.

Conclusions:

• Molecular weight and processing parameters are critical for controlling the shape memory effect in 4D printed PLA.
• Optimizing the glass transition temperature and selecting appropriate 3D printing conditions are essential for achieving desired shape transformations.
• Further research into 4D printing of PLA can unlock potential applications in areas requiring shape memory structures.