DLP 4D Printing of Programmable Molecularly-Engineered Liquid Crystal Elastomer Actuators

Area of Science:

• Materials Science
• Polymer Chemistry
• Additive Manufacturing

Background:

• Liquid crystal elastomers (LCEs) exhibit significant shape-changing capabilities crucial for soft actuators.
• Traditional methods like direct ink writing (DIW) for LCEs have limitations in resolution and geometric complexity.
• Digital light processing (DLP) offers high resolution but lacks intrinsic mesogen alignment for reversible actuation.

Purpose of the Study:

• To develop a scalable and versatile strategy for 4D printing LCEs using DLP.
• To enable programmable, large, and reversible actuation in complex LCE architectures.
• To establish DLP as a viable alternative to DIW for fabricating functional soft actuators.

Main Methods:

• A two-stage photo-crosslinking approach involving mechanical programming and subsequent photo-crosslinking.
• Utilizing DLP for high-resolution fabrication of partially cured LCE structures.
• Fixing mesogen alignment through controlled mechanical deformation before final photo-crosslinking.

Main Results:

• Fabrication of monodomain nematic LCEs with tunable thermo-mechanical properties.
• Achieved programmable, multimodal actuation strains up to 45% in complex architectures.
• Demonstrated consistent, reversible actuation over 100 thermal cycles in an octopus model.
• Showcased programming flexibility with stickman models exhibiting bending, twisting, and contraction.

Conclusions:

• The presented DLP-based strategy successfully overcomes limitations of existing methods for LCE 4D printing.
• This approach allows for precise control over mesogen alignment, leading to advanced actuator functionalities.
• The method offers significant design and programming flexibility, paving the way for novel soft robotic applications.