Programming sequential motion steps in 4D-printed hygromorphs by architected mesostructure and differential...

Area of Science:

• Materials Science
• Robotics
• Biomimetics

Background:

• Plant structures exhibit complex movements driven by environmental changes, offering inspiration for engineered systems.
• Hygromorphic materials change shape in response to moisture, enabling passive actuation.

Purpose of the Study:

• To present a method for programming the timescale and sequence of shape changes in 4D-printed hygromorphic structures.
• To demonstrate the potential of these programmable structures for advanced applications.

Main Methods:

• Utilized fused deposition modeling (FDM) 3D printing to create multi-layered, multi-material bilayers.
• Combined hygroscopic active layers with hydrophobic restrictive/blocking layers.
• Programmed motion timescale via mesostructure design (layer thickness, porosity) and printing parameters.

Main Results:

• Demonstrated control over motion timescale by adjusting active layer thickness, porosity, and blocking layer permeability.
• Achieved extended motion by increasing active layer thickness or blocking layer ratio.
• Showcased sequential motion in prototypes like a collision-avoiding aperture and a self-locking mechanism.

Conclusions:

• The developed method enhances programmability and functionality of hygromorphic 4D printing.
• This approach opens avenues for novel applications in robotics, smart actuators, and adaptive architecture.