Researchers from Tsinghua University, a Beijing-based research institution focused on engineering, optics, and artificial intelligence, together with collaborators from Zhejiang University’s medical research centers, report a volumetric 3D printing system capable of fabricating millimetre-scale objects in 0.6 seconds while maintaining a uniform 19 μm printing resolution across a 1 cm depth. Published in Nature, the method—Digital Incoherent Synthesis of Holographic Light Fields (DISH)—addresses the long-standing trade-off between spatial resolution and volumetric build rate in light-based additive manufacturing.
Volumetric approaches such as computed axial lithography form 3D objects by projecting light patterns from multiple angles into a stationary resin. High-resolution implementations typically require 360° sample rotation to avoid missing spatial frequencies in tomographic reconstruction. Mechanical rotation limits printing speed and complicates in situ fabrication. Increasing optical resolution further introduces diffraction constraints. A 0.055 numerical aperture objective at 405 nm has a depth of field of approximately 0.4 mm. Maintaining high-resolution intensity modulation across centimetre-scale volumes therefore requires axial scanning or reduced feature fidelity.
DISH replaces sample rotation with a rotating periscope that redirects patterned laser projections into a fixed resin container at up to 10 rotations per second. A digital micromirror device operating at up to 17,000 Hz synchronizes binary projection patterns with angular position. Instead of relying on ray-optics approximations used in earlier volumetric systems, the Tsinghua team implemented a wave-optics propagation model incorporating diffraction and refraction at the air–resin interface using angular spectrum methods. Coherent laser illumination enables holographic calculation of light fields that maintain high-resolution modulation far beyond the native focal plane of the projection optics, eliminating the need for mechanical focal shifting.
A coarse-to-fine holographic optimization algorithm first computes 180 greyscale angular dose distributions, then converts them into 1,800 binary projections using a binarization parameter G = 10 to reduce motion blur and preserve greyscale fidelity through incoherent summation. Adaptive optics–based calibration corrects single-pixel misalignment across projection angles. Fluorescence imaging from orthogonal cameras provides feedback for per-angle pattern adjustment.
Experimental validation demonstrated 11 μm optical dose distributions and uniform 19 μm printed feature sizes across a 1 cm axial range—more than twenty times larger than the 0.4 mm depth of field associated with the projection objective. Finest independent positive features measured 12 μm. Relief structures with designed linewidths of 10.8 μm were printed with measured widths of 11.0 ± 1.2 μm across the full centimetre depth. Multi-axis geometries, including a conch model with lines distributed along different z positions, maintained approximately 19 μm uniform resolution.
Printing throughput was quantified using a 200 mm³ volume fabricated in 0.6 seconds of exposure, corresponding to 333 mm³ per second. At a voxel size of (11 μm)² × 22 μm, voxel printing rate reached approximately 1.25 × 10⁸ voxels per second. Servo motor synchronization operated at 1,000 rpm with 1,800 binary projections per rotation cycle.
Short exposure duration mitigates gravitational drift during polymerization. Conventional volumetric systems often require high-viscosity materials between 6,000 and 10,000 cP to prevent sample sinking during multi-second exposures. DISH demonstrated compatibility with materials as low as 4.7 cP, including polyethylene glycol diacrylate aqueous solutions. Additional validated materials include dipentaerythritol hexaacrylate, bisphenol A glycerolate diacrylate, urethane dimethacrylate, gelatin methacrylate, and silk methacrylate hydrogels, spanning viscosities from single-digit to several hundred centipoise.
Successive production was demonstrated by integrating DISH with a fluidic channel, pump, and strainer system. Each object was exposed for 0.6 seconds before being displaced by controlled flow, enabling sequential fabrication of distinct geometries without mould changes. Demonstrated structures included lattice frames, hollow bifurcated tubes, helical channels, unsupported chain geometries, and detailed figurative models. X-ray computed tomography confirmed geometric fidelity between digital models and printed parts.
Single-side illumination introduces a missing-cone effect in Fourier space, slightly reducing axial resolution relative to lateral resolution. Authors note that alternative projection geometries could address this limitation. Speckle noise and dose contrast control for isolated microfeatures remain areas for further optimization.
Computational cost currently exceeds fabrication time. Holographic optimization for a 7.3 × 7.3 × 10 mm dataset required approximately 24 hours on a CPU using MATLAB. GPU acceleration and neural network-based hologram generation are proposed to reduce preprocessing time.
Volumetric additive manufacturing typically faces a resolution–throughput trade-off, as decreasing voxel size increases voxel count per unit volume and reduces build rate. Reported voxel printing rate combined with maintained centimetre-scale resolution demonstrates simultaneous improvement in both metrics relative to prior volumetric systems.
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Featured image shows Schematic illustrating DISH integrated with a fluidic channel, a pump and a strainer for mass production and collection of printouts in flow. Image via Nature.
