High-efficiency multi-scale holographic volumetric 3D printing with a phase light modulator.

Abstract

Light-based 3D printing with photocurable resins enables the rapid fabrication of complex structures with high resolution and fidelity. Tomographic Volumetric Additive Manufacturing (TVAM) employs a digital micromirror device (DMD) to project amplitude light patterns into rotating resin volumes, producing 3D geometries through photopolymerization. Typically, the light projection efficiency in such binary amplitude modulator-based systems is below a few percent. Recent advancements introduced phase encoding in TVAM using binary amplitude modulators and the Lee Hologram method, increasing axial control and boosting light efficiency to about 10%. In this work, we present the first 3D printing platform utilizing a phase light modulator (PLM), based on an array of micro-electro-mechanical piston mirrors. Compared to amplitude encoding, phase encoding with the PLM yields a 70-fold increase in laser power efficiency. By coupling this efficient light engine with a speckle reduction method in holographic volumetric additive manufacturing (HoloVAM), we experimentally demonstrate printing 3D objects across different scales from hundreds of micrometers to centimeters and with various materials from acrylate-based resins to soft hydrogels, including cell-laden hydrogels with a concentration of 1 million cells per mL. Micro-CT revealed a $~30.3\mu m$ as the smallest positive feature printed. Moreover, we introduce the use of gelatin Thiol/Norbornene as a material for printing with the Holographic VAM technique, which allows us to print large-scale objects (up to $(3\times 3\times 4{\mathrm{cm}}^3)$ within 2 minutes using only a 150 mW laser diode. The PLM opens up new avenues in volumetric AM for holographic techniques using low-cost single-mode laser diodes.