Engineering Strain-Stiffening Granular Hydrogels for 3D-Printed Tissue-Mimicry

Area of Science:

• Biomaterials Engineering
• Tissue Engineering
• Soft Matter Physics

Background:

• Biological tissues display nonlinear strain-stiffening, characterized by distinct toe (E_Toe) and heel (E_Heel) moduli, crucial for load-bearing.
• Synthetic materials currently lack a unified strategy for independently tuning these moduli while maintaining 3D printability.

Purpose of the Study:

• To introduce a 3D-printable strain-stiffening double-network granular hydrogel (SDGH).
• To enable region-specific control over E_Toe and E_Heel.
• To demonstrate the utility of SDGH in fabricating complex biological structures.

Main Methods:

• Developed a 3D-printable SDGH with tunable mechanical properties.
• Investigated the mechanism of strain-stiffening using in situ microscopic imaging and mechanical analysis.
• Utilized direct-ink writing to fabricate multilayered aortic valves with alternating soft and stiff inks.

Main Results:

• Achieved region-specific control of E_Toe and E_Heel by modulating secondary-network monomer concentration and microgel packing density.
• Elucidated the strain-stiffening mechanism.
• Successfully printed aortic valves with high geometric fidelity and excellent hemodynamic performance (regurgitation <1.2%), surpassing ISO 5840 standards.

Conclusions:

• The developed SDGH platform offers a generalizable design framework for creating customized tissue-mimetic organs.
• This technology holds significant potential for biomedical applications, particularly in synthetic surgical training materials.