Voxelated LC Patterning for Anisotropic 4D Freeform Printing
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Solution Overview
Problem
Existing 4D printing methods for liquid crystal elastomers (LCEs) are limited by high actuation temperatures, isotropic nature of thermal expansion, diffusion speed in hydrogels, and difficulty in spatially programming stimulus response, leading to materials that cannot achieve large, anisotropic, rapid, and reversible deformations necessary for autonomous smart systems.
Innovation Solution
A 4D-printing method using anisotropic magnetic susceptibility of LC monomers and spatially-selective photopolymerization with a digital micromirror device (DMD) to align molecular directors voxel-by-voxel, allowing for the fabrication of 3D free-form structures with independent control over molecular orientation and composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal expansion is used for shape change in printed structures, then the deformation can be programmed spatially, but the deformation magnitude is limited and the expansion is isotropic rather than anisotropic
Solution Approach 1:
The patent changes the physical parameter of the material by using liquid crystal elastomers instead of conventional thermally expanding materials. This enables anisotropic deformation with large magnitude while maintaining spatial programming capability through controlled thermal expansion in specific directions defined by the liquid crystal alignment.
Solution Approach 2:
The invention uses composite structures combining liquid crystal elastomers with conventional materials or internal architectures that enable both spatial programming and large anisotropic deformation. The composite approach allows integrating the directional properties of LCEs with the programmable expansion of traditional materials.
2Shape
If hydrogels are used for shape change, then large anisotropic deformation can be achieved, but the actuation speed is limited by diffusion speed and an aqueous environment is required
Solution Approach 1:
The patent replaces the diffusion-based actuation mechanism of hydrogels with a thermally-driven mechanism using liquid crystal elastomers. This substitution eliminates the need for aqueous environments and diffusion processes, enabling rapid actuation through direct thermal coupling while maintaining large anisotropic deformation capabilities.
Solution Approach 2:
The invention exploits the phase transition properties of liquid crystal elastomers, specifically the nematic-isotropic transition, to achieve rapid shape change. This phase transition mechanism is much faster than diffusion-based actuation and does not require aqueous environments, thereby resolving the speed limitation of hydrogels.
3Reliability
If LCEs are crosslinked in an aligned state to enable reversible shape change, then the material can undergo reversible deformation without external load, but it is difficult to program the stimulus response spatially
Solution Approach 1:
The patent segments the LCE structure into distinct regions with different liquid crystal alignments and crosslinking densities. This segmentation allows independent programming of stimulus response in each region while maintaining the reversibility of the overall structure. Different segments can be tailored to respond to stimuli in specific directions or at different thresholds.
Solution Approach 2:
The invention implements local quality variations by controlling the orientation and density of liquid crystal molecules and crosslinks in different spatial locations. This enables each local region to have customized stimulus response properties while the entire structure maintains reversible deformation capability through the inherent properties of LCEs.
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
Enables the creation of anisotropic macroscopic structures capable of large, reversible, and rapid shape changes in response to stimuli, suitable for applications like soft robots and aerospace systems, without requiring mechanical bias or aqueous environments.
Implementation Method 1
applying a magnetic field, having a first three-dimensional ('3D') magnetic field vector with respect to an origin point of a 3D coordinate system, to the first layer of first LC monomer or one or more of the plurality of voxels within the first layer of first LC monomer for a first dwell time, to produce in alignment with the first 3D magnetic field vector a first molecular director and/or first nematic alignment vector
Implementation Method 2
exposing the first layer of first LC monomer or the one or more of the plurality of voxels within the first layer of first LC monomer to a first dose of light radiation; wherein the first dose of light radiation has a wavelength, intensity and/or duration to polymerize the first layer of first LC monomer or the one or more of the plurality of voxels within the first layer of first LC monomer to a first polymerization depth
Data Source
AI summary
A four-dimensional (“4D”)-printing or 4D-additive manufacturing method for producing anisotropic macroscopic structures and/or anisotropic macroscopic materials having a plurality of voxels, comprising: providing or forming a first layer of a photocurable first liquid crystalline (LC) monomer; wherein the first layer of the first LC monomer has been provided or formed at a temperature falling within a nematic phase range of the first LC monomer; applying a magnetic field, having a first three-dimensional (“3D”) magnetic field vector with respect to an origin point of a 3D coordinate system, to the first layer of first LC monomer or one or more of the plurality of voxels within the first layer of first LC monomer for a first dwell time, to produce in alignment with the first 3D magnetic field vector a first molecular director and/or first nematic alignment vector within the first layer of first LC monomer or within each of the one or more of the plurality of voxels within the first layer of first LC monomer; exposing the first layer of first LC monomer or the one or more of the plurality of voxels within the first layer of first LC monomer to a first dose of light radiation.