Influence of micro-feature parameters of a constrained substrate on mass transfer of photopolymerization inhibition gas in continuous liquid interface production

Abstract

<p indent=0mm>The continuous liquid interface production (CLIP) process has dramatically improved the fabrication speed of 3D printing technology, which makes it possible for Stereolithography to be used for direct manufacturing of functional parts. The effect of the CLIP process is significant owing to the skillful application of the photopolymerization inhibition effect of oxygen; therefore, the mass transfer behavior of the oxygen across the substrate is the key factor affecting the thickness and stability of the inhibition zone. In this paper, a low-cost scheme for a constrained substrate with good oxygen permeability that is made of PDMS membrane has been proposed, and the paper focuses on the effect of PDMS membrane and microscopic pore characteristics on the oxygen mass transfer behavior in the substrate. Based on the calculation result of the oxygen-diffusion coefficient in the PDMS membrane through molecular dynamics simulation, the influencing factors and laws of oxygen permeability of substrate are numerically studied using COMSOL software. The substrates with oxygen permeability that was measured based on the constructed experiment device were fabricated. The results show that the PDMS membrane possesses good oxygen content and the diffusion coefficient of the content in the PDMS film is 4.018 ×10⁻⁵ cm²/s. The thickness of the PDMS film and the area ratio and diameter of the micro-pores in the supporting glass substrate affect the oxygen permeability. Reducing the thickness of the PDMS film, increasing the pore-area ratio, and reducing the micro-pore diameter facilitate the oxygen permeability improvement under the premise of meeting the strength requirements. The research results can provide process improvement direction and theoretical basis for the preparation of constrained substrates.