Liquid Crystalline Elastomer Alignment for Body-Temperature Actuation
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Solution Overview
Problem
Current LCE technologies require high temperatures for shape change, limiting their application in biomedical contexts where low temperatures are necessary, and achieving high actuation strain at physiologically relevant temperatures remains a challenge.
Innovation Solution
Synthetic and processing methods are employed to align polymer chains in the nematic state at low temperatures, below the nematic-to-isotropic transition temperature, and promptly crosslink them to achieve high strain without bias loads, using diacrylate monomers, dithiol spacers, and vinyl crosslinkers, with optional mechanical stretching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If current LCE technologies are used to achieve shape change, then high actuation strain can be obtained, but high temperatures are required which are not suitable for biomedical applications
Solution Approach 1:
The patent modifies the chemical composition and molecular structure of the LCE material to change its phase transition temperature from high temperatures to physiologically relevant temperatures (30-42°C). This is achieved by selecting specific liquid crystalline monomers with appropriate molecular weights and structures, thereby enabling shape change at safe body temperatures for biomedical applications
Solution Approach 2:
The patent creates a composite LCE system combining liquid crystalline monomers, crosslinking agents, and initiators to achieve both low transition temperature and high actuation strain. The composite formulation allows tuning of thermal and mechanical properties to simultaneously satisfy biomedical temperature requirements and performance requirements
2Reliability
If LCEs are processed at low temperatures to achieve physiologically relevant actuation, then biomedical applicability is improved, but achieving high strain without bias loads becomes difficult
Solution Approach 1:
The patent employs preliminary alignment of polymer chains during the curing process at low temperatures before the material is put into service. By using photopolymerization or other curing mechanisms that lock in the aligned state, the material achieves and maintains high strain capability without requiring continuous external bias loads, thus enabling biomedical applications
3Reliability
If high actuation strain is achieved at low temperatures, then biomedical relevance is improved, but the complexity of synthesis and processing increases
Solution Approach 1:
The patent divides the LCE synthesis into separate functional components (liquid crystalline monomers, crosslinking agents, initiators) that can be independently selected and optimized. This modular approach allows researchers to tune properties by mixing different components without redesigning the entire synthesis pathway, thereby reducing overall complexity while achieving physiologically relevant performance
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
LCE actuators demonstrate significant reversible shape change over a physiologically relevant temperature range of 30°C to 42°C, achieving up to 20% strain with minimal hysteresis and without external weights.
Implementation Method 1
the LCE should be processed at a temperature substantially lower than 30° C. By using processing conditions below room temperature, and more specifically below the Tni of the LCE, the polymer chains can be suitably aligned and the resulting LCE can achieve reversible shape change over a physiologically relevant temperature range
Implementation Method 2
exposing the extruded LCE precursor mixture to ultraviolet (UV) light to crosslink the LCE precursor mixture, thereby to yield the LCE in a nematic state
Data Source
AI summary
Provided herein are liquid crystalline elastomer (LCE) compositions capable of achieving high actuation strain in the narrow range of physiologically safe and relevant temperatures and methods of making the same. The methods disclosed herein leverage synthetic and processing approaches to achieve reversible shape change of LCE materials without the need for a bias load over the temperature range observed in contact with or inside the human body. The present methods utilize strategies to align the material polymer chains in their nematic state. By using processing conditions below a nematic-to-isotropic transition temperature (Tni) of the LCEs, the polymer chains can be suitably aligned and the resulting LCE can achieve reversible shape change over a physiologically relevant temperature range.