Ink Based on the Tunable Swollen Microsphere for a 3D Printing Hydrogel with Broad-Range Mechanical Properties

Area of Science:

• Materials Science
• Biomaterials Engineering
• Polymer Chemistry

Background:

• Developing effective 3D printing strategies for diverse functional monomers remains a significant challenge.
• Conventional 3D printed hydrogels often exhibit poor mechanical integrity (softness, fragility) due to a lack of energy dissipation mechanisms.

Purpose of the Study:

• To develop a microsphere-mediated ink preparation strategy for tailored rheological behavior in direct ink writing (DIW) of hydrogels.
• To enhance the mechanical properties and functionality of 3D printed hydrogels using chitosan microspheres as reinforcing agents.

Main Methods:

• A microsphere mediating ink preparation strategy was developed using chitosan microspheres (SCM).
• The tunable swelling of SCM under acid-driven electrostatic repulsion was utilized to control rheological properties.
• SCM were incorporated into hydrogels, acting as sacrificial bonds to improve mechanical strength and energy dissipation.

Main Results:

• The rheological behavior of SCM inks was independent of monomer type, allowing for broad compatibility.
• SCM inks demonstrated tunable mechanical properties, including strength (0.4-1.01 MPa), dissipated energy (0.11-3.25 MJ m⁻³), and elongation at break (47-626%).
• The developed inks enabled multi-functional integration for soft device production, including 4D printing robots and wearable strain sensors.

Conclusions:

• The microsphere mediating strategy offers a robust method for designing 3D printable hydrogels with tunable mechanical performance.
• This approach overcomes limitations of conventional hydrogels, paving the way for advanced soft devices.
• The strategy provides a new paradigm for creating functional hydrogels with enhanced mechanical robustness and diverse applications.