3D Printing Adhesion Reduction Using Photoinhibition
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Solution Overview
Problem
Photopolymer-based 3D printers face issues with adhesion between the window and the printed part due to uneven polymerization rates, leading to difficulties in separating the cured polymer from the window and increased mechanical forces during printing, which can result in print failures and material limitations.
Innovation Solution
The use of two light sources with different wavelengths to control photopolymerization and photoinhibition processes, creating a photoinhibition layer adjacent to the window and a photoinitiation layer between the window and the build plate, allowing for precise control of polymerization and reducing adhesion by inhibiting polymerization at the window-resin interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a PDMS window is used to reduce adhesion through oxygen permeability, then adhesion between polymer and window is reduced, but oxygen can be depleted from the PDMS and polymerization can subsequently occur at the interface
Solution Approach 1:
The patent changes the chemical parameters of the resin by incorporating photoinhibitor molecules that absorb actinic radiation and generate species which inhibit polymerization. This chemical modification ensures consistent polymerization inhibition at the window-resin interface regardless of oxygen depletion in PDMS windows.
Solution Approach 2:
The patent introduces photoinhibitor molecules as intermediary substances that mediate between the actinic radiation and the polymerization process. These molecules absorb the radiation and generate inhibiting species that prevent polymerization at the interface, acting as a chemical barrier similar to but more reliable than oxygen in PDMS windows.
2Productivity
If bottom-up illumination is used for photopolymerization, then polymerization rate is highest at the resin-window interface, but this causes adhesion between window and formed polymer
Solution Approach 1:
The patent applies local quality by creating spatially differentiated zones: a photoinhibited zone immediately adjacent to the window where polymerization is suppressed, and a photopolymerization zone further into the resin where curing occurs. This is achieved by positioning the photoinhibitor concentration and actinic radiation intensity to create a gradient effect.
Solution Approach 2:
The patent applies preliminary anti-action by pre-establishing a photoinhibited layer at the window-resin interface before photopolymerization begins. The photoinhibitor molecules are present in the resin and immediately begin inhibiting polymerization when exposed to actinic radiation, preventing adhesion before it can occur.
3Device complexity
If standard optical window materials are used instead of PDMS, then device complexity is reduced, but adhesion forces increase due to lack of oxygen permeability
Solution Approach 1:
The patent replaces the mechanical/physical solution of using PDMS windows with oxygen permeability with a chemical solution using photoinhibitor molecules. This substitution allows the use of standard optical window materials while maintaining polymerization inhibition through chemical means rather than relying on material permeability properties.
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 approach reduces adhesion forces, minimizes mechanical stress on the print, and allows for the use of standard optical window materials, increasing print reliability and flexibility in photopolymer formulations, while avoiding the need for complex separation mechanisms.
Implementation Method 1
directing a first light through the window into the liquid, the first light having a first wavelength selected to produce photoinhibition
Implementation Method 2
creating a solid structure on the build plate from the photoactive resin within a photoinitiation layer of the liquid by directing a second light through the window into the liquid
Data Source
AI summary
Methods, systems, and apparatus, including medium-encoded computer program products, for three dimensional print adhesion reduction using photoinhibition include, in one aspect, a method including: moving a build plate in a vat of liquid including a photoactive resin; creating a photoinhibition layer within the liquid directly adjacent a window of the vat by directing a first light through the window into the liquid, the first light having a first wavelength selected to produce photoinhibition; and creating a solid structure on the build plate from the photoactive resin within a photoinitiation layer of the liquid by directing a second light through the window into the liquid, where the photoinitiation layer resides between the photoinhibition layer and the build plate, and the second light has a second wavelength different than the first wavelength.