High-Performance Sunlight-Induced Polymerized Hydrogels and Applications in 3D and 4D Printing

Area of Science:

• Polymer Chemistry
• Materials Science
• Photochemistry

Background:

• Limited reports exist on water-soluble photoinitiating systems for hydrogel formation.
• Developing efficient photoinitiators is crucial for advanced polymerization techniques.

Purpose of the Study:

• To synthesize a novel, highly water-soluble organic dye as a photoinitiator.
• To investigate its photoinitiation ability in hydrogel formulations under sunlight.
• To explore the photochemical mechanism and hydrogel properties for 3D/4D printing applications.

Main Methods:

• Synthesis of a water-soluble organic dye photoinitiator.
• Real-Time Fourier Transform Infrared (RT-FTIR) spectroscopy for photopolymerization kinetics.
• UV-visible absorption, fluorescence spectroscopy, steady-state photolysis, fluorescence quenching, and cyclic voltammetry for mechanism elucidation.
• Characterization of hydrogel properties (water content, swelling).

Main Results:

• The synthesized water-soluble photoinitiator demonstrated high efficiency at a low concentration (0.01 wt%).
• Hydrogel formulations achieved nearly 100% double bond conversion under sunlight.
• Successful 3D printing of objects with smooth surfaces and high spatial resolution.
• Demonstrated reversible shape-changing behavior for 4D printing applications.

Conclusions:

• The novel water-soluble photoinitiator is highly effective for sunlight-polymerized hydrogels.
• The developed hydrogels are suitable for advanced 3D and 4D printing, including bioprinting.
• This work expands the potential of water-soluble photoinitiators in materials science and biomedical engineering.