Pluralizing actuation behavior of 3D printable liquid crystal elastomers via polymerization sequence control.

Area of Science:

• Materials Science
• Polymer Chemistry
• Soft Robotics

Background:

• Mechanical stretching is standard for aligning mesogens in liquid crystal elastomers (LCEs), crucial for muscle-like actuation.
• Conventional LCEs primarily exhibit cooling-induced elongation due to mesogen alignment solely in the stretching direction.

Purpose of the Study:

• To design a novel LCE architecture enabling tunable actuation modes.
• To achieve complex, multimodal four-dimensional (4D) actuation in LCEs.

Main Methods:

• Fabrication of an interpenetrating double network LCE comprising an LCE network and an elastomer network.
• Sequential polymerization of the two networks, with one network pre-stretched before the other's polymerization.
• Integration with 3D printing to create geometrically complex LCE structures.

Main Results:

• The double-network LCE demonstrated two opposite actuation modes: conventional cooling-induced elongation and unusual cooling-induced contraction, dependent on the polymerization sequence.
• Strategic combination of these opposite behaviors within a single LCE resulted in sophisticated actuation capabilities.
• 3D printing enabled the creation of complex LCEs exhibiting diverse multimodal 4D actuation.

Conclusions:

• The developed double-network LCE design expands the possibilities for LCE actuator development.
• This approach offers new avenues for creating advanced LCE actuators with tailored and complex actuation behaviors.
• The findings hold potential for diverse applications in soft robotics and smart materials.