Holographic 3D Printing

For light, holograms will be realized by static/dynamic phase masks, diffractive optical elements, or optical metasurfaces. Some of these can be realized by 3D laser nanoprinting. To expose a volumetric structure by the 3D light field that results from a plane-wave passing through this hologram, theory needs to solve an inverse problem to compute the hologram – a first challenge. A physics challenge lies in realizing the holograms with sufficient accuracy. A chemistry challenge lies in that the exposed two-photon photoresist needs to be sufficiently sensitive such that the energy of a single optical femtosecond suffices to polymerize the entire volume of the structure. We expect that deep sub-µm voxel sizes can be 3D printed at peak rates exceeding 10²⁰ voxel/s – many orders of magnitude faster than the current state-of-the-art of 10⁸ voxel/s.

For ultrasound, the physics is analogous. Using static ultrasound holograms, forces have already been exerted onto larger entities such as biological cells, which can thereby be assembled into organoid-like architectures. A theory and physics challenge now lies in realizing dynamic ultrasound holograms. Thereafter, flexible “single-shot” 3D assembly of biological structures with overall dimensions up to one centimeter appears to be in reach.