Triplet-Triplet Annihilation Upconversion Photopolymerization
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Solution Overview
Problem
Current three-dimensional printing techniques based on photopolymerization, such as multiphoton and continuous-wave laser methods, are limited by high irradiance requirements and slow manufacturing speeds, making them unsuitable for industrial-scale production of larger objects with submicron resolution.
Innovation Solution
A novel nonlinear photopolymerizable composition using a triplet photosensitizer, annihilator, and photoinitiator that employs a triplet-triplet annihilation upconversion (STTA-UC) mechanism, allowing photopolymerization with lower excitation light irradiances, enabling controlled three-dimensional irradiation zones and continuous light sources for efficient 3D printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiphoton photopolymerization is used to achieve submicron spatial resolution, then manufacturing precision is improved, but productivity deteriorates due to slow linear manufacturing speeds (a few cm/s) and volume manufacturing speeds (several hours per mm3)
Solution Approach 1:
The patent segments the photopolymerization process into two distinct stages: first, a photoinitiator absorbs UV light to generate radicals that initiate polymerization; second, a separate photosensitizer absorbs visible or near-IR light to generate additional radicals that propagate and accelerate polymerization. This segmentation allows each component to be optimized for its specific function and enables the use of lower-power, more efficient light sources.
Solution Approach 2:
The patent introduces a photosensitizer as an intermediary substance that mediates between the visible/near-IR light source and the photoinitiator system. The photosensitizer absorbs lower-energy photons and transfers energy to generate radicals, acting as a bridge that enables the use of more efficient, lower-power light sources while maintaining polymerization effectiveness.
2Manufacturing precision
If powerful pulse lasers with high irradiance (TWatt/cm2) are used to achieve multiphoton photopolymerization, then manufacturing precision is improved, but use of energy deteriorates due to extremely high power requirements
Solution Approach 1:
The patent fundamentally changes the irradiance parameter from TWatt/cm2 to much lower levels by utilizing a two-photon absorption mechanism with separate photoinitiator and photosensitizer components. This parameter change enables the use of continuous-wave or pulsed lasers with moderate power, dramatically reducing energy consumption while maintaining submicron spatial resolution through the nonlinear absorption characteristics of the dual-component system.
3Productivity
If continuous-wave laser methods are used to reduce manufacturing time, then productivity is improved, but manufacturing precision deteriorates because object dimensions remain very limited (a few tens of micrometers)
Solution Approach 1:
The patent creates a composite photopolymerization system combining a photoinitiator and photosensitizer with distinct absorption spectra. The photoinitiator responds to UV light for precise spatial control, while the photosensitizer responds to visible or near-IR light for deeper penetration and faster polymerization. This composite approach enables continuous-wave laser processing with both improved productivity and maintained precision.
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 photopolymerization at significantly lower irradiances (e.g., 0.1 W/cm2) compared to existing techniques, facilitating the development of 3D printing on an industrial scale with improved manufacturing speeds and resolution, while minimizing the inhibiting effects of oxygen.
Implementation Method 1
the photosensitizer being capable of absorbing an excitation light signal received in a first range of wavelengths
Implementation Method 2
the annihilator being capable of emitting a light signal in a second range of wavelengths different from the first range of wavelengths, a photon energy of the light signal emitted by the annihilator being greater than a photon energy of the light signal received by the photosensitizer
Implementation Method 3
the annihilator is capable of implementing an energy transfer mechanism in order to excite the photoinitiator for polymerization of the resin
Implementation Method 4
the excited photoinitiator is capable of generating at least one polymerization initiator able to cause a polymerization reaction of the resin
Data Source
AI summary
A photopolymerizable composition comprises at least a polymerizable resin, a photosensitizer, an annihilator, and a photoinitiator. The photosensitizer is formulated to absorb an excitation light signal received in a first range of wavelengths. The annihilator is formulated to emit a light signal in a second range of wavelengths different from the first. During the absorption of light by the photosensitizer in the first range of wavelengths, the annihilator emits a light signal in the second range, a photon energy of the emitted light signal being greater than a photon energy of the light signal received by the photosensitizer. The annihilator is also formulated to implement an energy transfer mechanism to excite the photoinitiator for polymerization of the resin. The excited photoinitiator is formulated to generate at least one polymerizable initiator to cause the polymerization reaction. Related methods, such as three-dimensional printing methods, and materials are also disclosed.