Home-Researchers develop sub-second volumetric 3D printing method using holographic light fields
Researchers atTsinghua Universityhave developed a volumetric 3D printing method that produced millimetre-scale polymer structures in as little as 0.6 seconds. Called digital incoherent synthesis of holographic light fields (DISH), the method uses holographically optimized light projections delivered through a high-speed rotating periscope, removing the need to rotate the resin container during printing.
Published inNature, the research addresses the trade-off between resolution and volumetric build rate in additive manufacturing. Using a 0.055-NA objective, the team reports a stable printing resolution of around 19 μm across a 1 cm range, with the finest independent positive features measuring approximately 12 μm. The method was demonstrated using several acrylate-based and hydrogel materials, including PEGDA, DPHA, BPAGDA, GelMA, SilMA, and UDMA.
Volumetric additive manufacturing forms complete 3D objects by controlling light dose throughout a volume of photosensitive material. Existing methods such as computed axial lithography can produce complex parts without the layer-by-layer process used in stereolithography or digital light processing. However, many systems rely on rotating the sample to deliver projections from multiple angles. This can limit speed, introduce alignment issues, and make in situ printing harder to implement.
DISH avoids this by keeping the container fixed and rotating the projection path instead. A digital micromirror device (DMD) generates light patterns at high speed, while a periscope placed in front of the objective lens changes the projection angle. The DMD patterns are synchronized with the rotation angle, allowing multiple light fields to combine inside the resin and form the target 3D dose distribution.
The researchers used a coherent 405 nm laser source and a wave-optics-based algorithm to calculate the projected light fields. This was necessary because, at higher resolution, diffraction and defocus effects become significant. According to the paper, this enabled high-resolution modulation across a depth range of up to 1 cm using the 0.055-NA objective, more than 20 times larger than its native depth of field.
Holographic optimization enables high-resolution volumetric printing
To produce the required 3D light distributions, the team developed a coarse-to-fine iterative algorithm. The first stage calculates coarse 3D dose distributions for different projection angles. The second stage refines groups of binary DMD patterns using a holographic propagation model that accounts for wave optics and refraction at the air-material interface.
The authors compared their method with previous penalty minimization approaches used in computed axial lithography and with a global Gerchberg–Saxton algorithm. In simulations, DISH produced more accurate 3D dose distributions, measured using the Jaccard index and signed distance errors. The researchers selected 1,800 binary projections per rotation cycle for practical experiments, corresponding to 180 coarse 3D dose distributions.
Because high-speed, high-resolution volumetric printing is sensitive to optical errors, the researchers also developed an adaptive-optics-based calibration method. Fluorescent images captured by two orthogonal cameras were used to detect beam misalignment, allowing the DMD patterns for each projection angle to be shifted and corrected. The paper states that this calibration process can be completed within a few minutes and does not require hardware modification once the system is fixed.
Source: 3D Printing Industry
