Multi-material 3D Printing of Mechanochromic Double Network Hydrogels for On-Demand Patterning

Area of Science:

• Materials Science
• Soft Robotics
• Biomimicry

Background:

• Cephalopods utilize skin chromatophores for dynamic color and pattern changes, primarily for camouflage.
• Replicating such sophisticated color-changing abilities in synthetic soft materials presents significant fabrication challenges, particularly for achieving arbitrary patterns and shapes.

Purpose of the Study:

• To develop a novel method for fabricating mechanochromic soft materials with complex geometries.
• To create 3D hydrogel structures capable of exhibiting color changes in response to mechanical stimuli.

Main Methods:

• A multi-material direct ink writing (DIW) 3D printing technique was employed.
• Microparticles were prepared by grinding freeze-dried polyelectrolyte hydrogels containing mechanophores.
• These microparticles were immobilized in a precursor solution to form a printable ink, with properties tuned by grinding time and concentration.

Main Results:

• Various 3D hydrogel structures with arbitrary patterns and shapes were successfully fabricated using the DIW printing method.
• The printed hydrogel structures demonstrated mechanochromic properties, exhibiting color changes upon applied force.
• The microgel ink's rheological and printing characteristics were effectively controlled.

Conclusions:

• The microgel printing strategy offers a promising approach for fabricating custom-shaped mechanochromic devices.
• This technique holds potential for applications requiring adaptive, stress-responsive color-changing materials.