Optically Fixable Shape Memory Polymers via Azobenzene Photoisomerization
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Solution Overview
Problem
Current light-activated shape memory polymers (SMPs) require lengthy UV exposure and have limited fixity, making them inefficient for remote and spatial control applications, and lack the ability to combine thermal and optical shape memory.
Innovation Solution
Development of glassy, photoresponsive polymeric materials using covalently attached azobenzene units that can be optically fixed with short exposures to eye-safe 442 nm light, enabling rapid and indefinite shape retention through trans-cis-trans reorientation of azobenzene chromophores, and combining with thermal shape memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV light exposure is used to fix shape in light-activated SMPs, then shape fixing capability is achieved, but exposure time is lengthy and fixity is limited
Solution Approach 1:
The patent changes the wavelength parameter of light from traditional UV to visible blue light (442 nm), which has higher energy and enables faster photoisomerization. This parameter change reduces exposure time from hours to seconds while improving shape fixity and enabling indefinite shape retention
Solution Approach 2:
The patent creates a composite polymer network incorporating azobenzene chromophores covalently bonded to the polymer backbone. This composite structure combines the shape memory properties of polymers with the photoresponsive properties of azobenzene, enabling rapid and indefinite shape fixing under visible light
2Ease of operation
If photoinduced changes to crosslink density are used to program shape, then shape memory is achieved, but spatial control and remote control capability are limited
Solution Approach 1:
The patent replaces mechanical or thermal control systems with optical control using visible light. The azobenzene chromophores respond directly to light irradiation, enabling wireless remote control and spatially selective shape programming through masking or holographic exposure without complex control mechanisms
Solution Approach 2:
The patent creates a multi-functional material that responds to both thermal stimuli and optical stimuli. The material can be controlled remotely via light while maintaining thermal shape memory capabilities, providing versatile control options without requiring separate control systems
3Adaptability or versatility
If thermal shape memory is used, then shape recovery is achieved, but combination with optical shape memory is not possible
Solution Approach 1:
The patent merges thermal shape memory and optical shape memory into a single polymer network. The azobenzene-containing polymer backbone provides both thermal responsiveness (through glass transition) and optical responsiveness (through photoisomerization), enabling dual shape memory capability in one material system
Solution Approach 2:
The patent creates a composite polymer network where azobenzene chromophores are covalently integrated into the polymer backbone. This composite structure enables simultaneous thermal and optical shape memory functionality without requiring separate material layers or complex multi-component systems
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
The materials achieve high-performance, bidirectional shape memory with rapid optical fixing and long-term retention of both optically and mechanically induced strains, with the ability to combine thermal and optical fixing, allowing for precise control and extended durability.
Implementation Method 1
trans-cis-trans reorientation of azobenzene chromophores
Implementation Method 2
heating the polymeric material above a transition temperature, which can be the glass transition (Tg)
Implementation Method 3
Shape memory polymers (SMPs) are stimuli-responsive materials that remember an original, so-called 'permanent shape' that can be recovered from a temporary fixed shape by exposure to external stimuli
Data Source
AI summary
This application discloses a method of photomechanically manipulating optically fixable SMPs that employ glassy, photoresponsive polymeric materials, which are capable of rapid optical-fixing with short exposures (<<5 min) of eye-safe visible light. Key to the optical fixing is the use of polymeric materials composed of covalently attached photochromic units such as azobenzene and the use of light capable of inducing simultaneous trans-cis and cis-trans isomerization of azobenzene or other photochromic moieties capable of similar cycling. Upon exposure to light in this wavelength regime (440-514 nm for the azobenzene unit here), real and lasting reconfigurations are induced capable of fixing both the optically induced strain as well as mechanically induced strain. A linear dependence of bending angle on polarization angle is observed and may be used to control the shape reconfiguration of the SMPs.