Tunable Liquid Crystal Interface for Enhanced Surface Smoothness and Functional Properties in LCD Vat Photopolymerization

Liquid crystal display (LCD) vat photopolymerization (VPP) is gaining popularity in both industry and research due to its cost‐effectiveness compared to other polymer‐based 3D printing methods. However, surface quality remains a critical limitation, primarily due to the black matrix present between the active pixels of the LCD panel. Pixelation and staircase effects significantly degrade the surface finish and functional performance of printed parts. In this study, a voltage‐tunable polymer‐dispersed liquid crystal (LC) film is introduced as a secondary optical interface between the LCD panel and the resin vat. By varying the input voltage, the LC film enables tunable light scattering, diffuses sharp pixel boundaries, and smooths the projected mask image. This results in up to 95% reduction in surface roughness compared to the standard No LC condition. Improved surface smoothness enhances interlayer bonding, reduces stress concentration zones, and leads to substantial gains in tensile and flexural strength, including energy absorption. Additionally, the light transmittance of printed parts improves without post‐processing. A resolution study confirms that features down to 2‐pixel width remain resolvable, satisfying the Rayleigh criterion. This scalable and hardware‐compatible strategy effectively enhances surface quality and mechanical performance in LCD VPP without compromising resolution.