Inherently Porous 3D Polymer Objects via Phase Separation
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Solution Overview
Problem
Existing 3D printing methods for porous polymers rely on templating techniques that increase synthetic complexity, stability issues, and lead to optically inhomogeneous reaction media due to template removal difficulties and light scattering, making them unsuitable for effective pore formation.
Innovation Solution
Combining stereolithography or two-photon 3D direct laser writing with polymerization-induced phase separation using a suitable solvent as a porogen to create inherently porous 3D structures, where a mixture of photoactive monomers, porogen solvents, and photoinitiators is used to print structures that are then immersed in a solvent to remove unreacted components, allowing for tuning of pore size and porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If templating techniques are used for pore formation in 3D printing, then porous structures can be created, but synthetic complexity increases and template removal becomes difficult
Solution Approach 1:
The patent extracts the harmful templating step entirely from the process. Instead of adding templates that must be removed, the invention uses porogen solvents that are miscible with monomers but immiscible with polymers, allowing pores to form naturally during polymerization without requiring subsequent template removal steps.
Solution Approach 2:
The patent inverts the conventional approach by not trying to create pores through template removal, but rather by preventing polymer formation in specific regions through phase separation. The porogen solvents naturally segregate during polymerization, creating pore spaces without requiring external templates.
2Manufacturing precision
If templates are used for pore formation, then porous structures can be created, but template removal leads to stability issues
Solution Approach 1:
The porogen solvents perform the dual function of both creating pores and maintaining structural stability. They are selectively removed after polymerization, leaving behind a stable porous network that was self-formed during the polymerization process itself, eliminating the need for separate template stabilization steps.
3Manufacturing precision
If templates are added to photoresist, then pores can be formed, but the reaction medium becomes optically inhomogeneous causing light scattering
Solution Approach 1:
The patent maintains homogeneity during the critical polymerization stage by using porogen solvents that are completely miscible with monomers, creating a uniform reaction medium that does not scatter light. The phase separation and pore formation occur only after polymerization is complete, during the solvent removal stage.
4Manufacturing precision
If templating methods are used, then porous structures can be created, but the process requires additional steps increasing manufacturing time
Solution Approach 1:
The patent merges pore formation with the polymerization process itself. The porogen solvents are incorporated into the photoresist mixture from the beginning, and pores form automatically during polymerization through phase separation, eliminating the need for separate template addition, placement, and removal 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 method enables the production of inherently porous 3D structures with controlled pore sizes and porosity, avoiding the limitations of templating methods, and results in structures with improved optical homogeneity and printing efficiency.
Implementation Method 1
stereolithography is a photochemical process where a light source (a laser or projector) induces a chemical reaction in the photoresist, mediated by a molecule known as a photoinitiator that is mixed into the resist at concentrations of around 1%. The reaction converts the monomers in the liquid photoresist into cross-linked solid polymers.
Implementation Method 2
Polymerization induced phase-separation is the occurrence of phase separation in a multicomponent mixture induced by the polymerization of one or more components. The increase in molecular weight of the reactive component renders one or more components to be mutually immiscible in one another, resulting in spontaneous phase segregation
Data Source
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AI summary
The present invention relates to printing of inherently porous 3D polymer objects using a template-free 3D printing method. During the printing process, projection stereolithography or two-photon 3D direct laser writing is combined with photopolymerization-induced phase separation using a suitable solvent as porogen. The pore size, porosity and chemical functionality of the 3D structures can be readily tuned by adjusting the photoresist compositions. It is possible to prepare porous 3D structures with pore sizes in the meso- and macro-range having specific geometries and architectures.