Reversing Multicolor Tomography for Precise Property Control in Ultrafast 3D Printing

Multiscale structures are gaining significant importance in catalysis, biomimetics and mechanical engineering. These structures show characteristic features spanning a few orders of magnitude in length and are often difficult to build because of their geometric complexity. 

3D printing allows high design freedom and is the most promising means of building such structures. However, current 3D printing methods are predominately voxelated, i.e. building objects point-by-point or layer-by-layer.


The printing time scales proportionally to the number of voxels and thus exponentially with workpiece size: e.g. a 1 dm3 object with mm-scale features contains at least 1015 voxels – an astronomical number for any existing AM machine to handle within a reasonable timeframe.


Moreover, voxelated methods rely on the cumbersome switching of resins to realize property variations inside a workpiece.4 This strategy offers a limited number of property grades and a relatively low spatial resolution for property customization. The next generation of AM will require 1) severing the link between printing time and the number of voxels and 2) a high degree of control over internal property variation. Here we exploit the well-established mathematical framework of CT to realize both goals in one shot.


Conventional adhesive manufacturing (AM) methods are not adequate in building workpieces with multiscale features because of the slow speed and the limited capacity to realize internal property variation with high precision. Here we present a novel 3D printing strategy that offers two unique features:


  1. Ultrafast construction of multiscale structures
  2.  Precise control of internal property variation

The new method, based on physically reversing computed tomography (CT) and a synergistic use of multicolor projections on photoresponsive polymers, will enable the construction of moderate-sized workpieces (up to ~10 cm in diameter) with microstructural features (~100 µm or less) in less than a minute, while offering stiffness control on a voxel-to-voxel basis.


Yi Yang
Associate Professor
DTU Chemistry