Development of open-architecture two-wavelength grayscale digital light processing for advanced vat photopolymerization

Vat photopolymerization (VPP) is an additive manufacturing technique that creates 3D parts by projecting 2D images onto layers of photopolymer resin. These images are often delivered using digital light processing (DLP) systems with digital micromirror devices. While conventional VPP relies on a single-wavelength DLP system, recent advancements have introduced multi-wavelength approaches to selectively trigger distinct photochemical reactions, enhancing multi-material printing and geometric precision. To further advance multi-wavelength VPP, open-architecture two-wavelength DLP systems are essential for enabling real-time control with adaptive exposure masks. In this work, we develop an orthogonal two-wavelength grayscale DLP system featuring custom optics and a reconfigured field-programmable gate array (FPGA)-based control circuit. The system integrates a 50/50 beam-splitting optical architecture that merges 365 nm and 460 nm light sources, ensuring minimal distortion and precise alignment. A high-resolution CMOS camera and power meter are used to quantify the accuracy and alignment of the two-wavelength exposure masks. A workflow for projection alignment and calibration, grayscale image generation, compensation, and bit-stream data transmission via FPGA programming is established, enabling high-resolution, precisely aligned, and spatially accurate two-wavelength grayscale intensity projections onto the build platform. The system’s performance is validated through ray-tracing simulations, optical characterizations, and experimental sample printing. The developed architecture facilitates integration with mechanized platforms, metrology tools, and process control technologies, providing a robust foundation for reproducible and precise two-wavelength VPP. The elaborate methodologies of optics design, FPGA programming, and image processing advance both existing and emerging multi-wavelength VPP technologies, enhancing their capability for complex material systems and sophisticated applications.