Dip-Coating-Assisted Polytetrafluoroethylene Vat Photopolymerization 3D Printing: Optimization of Macro/Micro-Surface Defects and Enhanced Fabrication Efficiency

Vat photopolymerization 3D printing offers an effective route for fabricating complex poly(tetrafluoroethylene) (PTFE) components. However, the surface quality of printed parts is severely deteriorated by the combined effects of macro-scale staircase effect inherent to the layer-by-layer printing process and microscale surface roughness characteristics induced by thermal debinding. Dip-coating was adopted in this study, as it offers a practical and accessible means to improve the surface quality of components. However, achieving effective coverage and smoothing of both the macroscopic staircase effect and microscopic surface roughness characteristics remains challenging. To address this issue, a two-step dip-coating process was developed using photocuring PTFE slurry and its dispersion without the introduction of foreign materials. By precisely controlling the withdrawal speed and modifying the surface properties of the components, uniform coverage and deposition of the liquid film over both stepped and rough surfaces were achieved, ultimately yielding PTFE components with submicrometer-level surface roughness. Furthermore, by leveraging the responsiveness of dip-coating film thickness to surface roughness, which is attributed to the adhesion-dominated bilayer liquid film structure on texture surfaces, a printing strategy that combines large layer thickness curing with dip-coating is proposed. This strategy enhances printing efficiency by approximately 50% while maintaining a high surface quality. Therefore, this study provides a method for surface quality optimization in vat photopolymerization of PTFE, with potential for application to materials such as ceramics and metals.