Stereolithography Photoalignment of Liquid Crystal Elastomers
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Solution Overview
Problem
Current additive manufacturing techniques for liquid crystal elastomers (LCEs) are limited in achieving high part resolution, increased part complexity, and 180° liquid crystal alignment control within local volume elements, which restricts 3D-to-3D shape change capabilities, particularly in forming complex shapes like octet truss and gyroid structures, and lack precise layer-by-layer printing with controlled LC alignment.
Innovation Solution
The development of a method using stereolithography (SLA) with photoalignment techniques to form 3D structures by aligning liquid crystal elastomers voxel-by-voxel with polarized light, allowing for multiple regions of LCs to be aligned in different orientations, enabling reversible shape changes in response to environmental stimuli, with a maximum dimension of aligned regions less than 60 microns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct ink write (DIW) additive manufacturing is used to print LCEs, then material deposition and layer formation are achieved, but part resolution and liquid crystal alignment control are limited
Solution Approach 1:
The patent replaces the mechanical extrusion-based DIW system with a photopolymerization-based stereolithography system. Instead of mechanically depositing LCE material layer by layer, the invention uses UV light to selectively cure liquid crystal monomer compositions, enabling precise spatial control of LC alignment through photopolymerization while maintaining ease of manufacturing through vat polymerization processes
Solution Approach 2:
The invention changes the fundamental parameter of material state from deposited polymer (DIW) to liquid monomer (stereolithography). This allows the liquid crystal monomers to be optically aligned before polymerization, achieving superior LC alignment control and part resolution while the photopolymerization process maintains manufacturing simplicity through standard SLA equipment
2Adaptability or versatility
If DIW techniques are used for LCE printing, then unidirectional alignment is achieved, but 3D-to-3D shape change capability is restricted
Solution Approach 1:
The patent transitions from 2D unidirectional alignment achievable by DIW to 3D multi-directional alignment through stereolithography. The photopolymerization process enables independent control of LC orientation in three-dimensional space by varying the polarization and angle of UV exposure, allowing complex 3D-to-3D shape changes while maintaining precise alignment control through optical field manipulation
Solution Approach 2:
The invention introduces dynamic control of LC alignment during the printing process. By adjusting polarization filters and light source angles in real-time during photopolymerization, the system can adaptively set different LC orientations in different spatial locations, enabling versatile 3D-to-3D shape change capabilities while preserving manufacturing precision through programmable optical control
3Manufacturing precision
If lithography techniques are used to print LCEs, then layer-by-layer printing is achieved, but LC alignment control is absent
Solution Approach 1:
The patent employs self-alignment of liquid crystal monomers during the photopolymerization process. The liquid crystal monomers inherently align with the polarization direction of the UV light before curing, eliminating the need for separate alignment steps. This self-service alignment mechanism achieves precise LC alignment control while maintaining ease of manufacture through standard stereolithography processes
Solution Approach 2:
The invention performs preliminary alignment of liquid crystal monomers to the desired orientation before polymerization occurs. By exposing the liquid crystal monomer composition to polarized UV light at controlled angles during the printing process, the monomers pre-align to the target configuration, and subsequent polymerization locks this alignment in place, achieving precise LC alignment control through integrated optical-preparation steps
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the creation of 3D structures with high actuation strain percentages, up to 50%, and allows for complex shape changes in multiple directions, overcoming the limitations of direct ink write methods by achieving precise LC alignment and increased part complexity.
Implementation Method 1
stereolithography (SLA) with photoalignment techniques to form 3D structures by aligning liquid crystal elastomers voxel-by-voxel with polarized light
Implementation Method 2
The liquid crystal elastomers in a portion of a first of the layers are substantially aligned in a predefined first orientation and the liquid crystal elastomers in a portion of a second of the layers are substantially aligned in a predefined second orientation that is different than the first orientation
Data Source
AI summary
A product includes a three-dimensional structure having a plurality of sequentially-formed layers comprised of liquid crystal elastomers. The liquid crystal elastomers in a portion of a first of the layers are substantially aligned in a predefined first orientation and the liquid crystal elastomers in a portion of a second of the layers are substantially aligned in a predefined second orientation that is different than the first orientation. Each of the portions of the three-dimensional structure is characterized as exhibiting a shape change in response to a stimulus, wherein the shape change is reversible. The product includes a contiguous region of aligned liquid crystal elastomers in one of the portions having a maximum dimension of less than 60 microns.