Acoustodynamic Covalent Materials Engineering for the Remote Control of Physical Properties Inside Materials.

Area of Science:

• Polymer Chemistry
• Materials Science
• Additive Manufacturing

Background:

• Vat photopolymerization (VP) 3D printing (3DP) offers high precision but struggles with dynamic material property manipulation.
• Cross-linked polymers from VP-3DP are typically insoluble and infusible, limiting post-fabrication modifications.
• Developing methods to introduce dynamic functionalities into 3D-printed materials is crucial for advanced applications.

Purpose of the Study:

• To fabricate light- and high-intensity focused ultrasound (HIFU)-responsive cross-linked polymeric materials using VP-3DP.
• To introduce reversible cross-links into 3D-printed objects via hexaarylbiimidazole (HABI) chemistry.
• To demonstrate the ability to tune physical properties, enable pinpoint modification, healing, and reshaping of 3D-printed materials.

Main Methods:

• Utilized vat photopolymerization (VP) 3D printing (3DP) to fabricate cross-linked polymers.
• Incorporated hexaarylbiimidazole (HABI) into polymer chains to enable light- and HIFU-responsiveness.
• Investigated the orthogonal photochemistry of HABI and photopolymerization for reversible cross-linking.
• Applied photostimulation and high-intensity focused ultrasound (HIFU) to induce material responses.

Main Results:

• Successfully fabricated 3D-printed objects with HABI-derived reversible cross-links.
• Demonstrated that photostimulation triggers responses primarily at the surface by generating triphenylimidazolyl radicals (TPIRs).
• Showcased HIFU's ability to induce cleavage and responses within the interior of the materials, even beyond obstacles.
• Confirmed the orthogonality of HABI photochemistry and photopolymerization, allowing for controlled cross-linking.

Conclusions:

• The developed system enables the creation of dynamic, responsive 3D-printed polymeric materials.
• HIFU offers superior penetration and control compared to photostimulation for modifying HABI-embedded polymers.
• This technology holds significant potential for tuning material properties, recycling, pinpoint modification, healing, and reshaping of 3D-printed objects.