Controlling Light in Scattering Materials for Volumetric Additive Manufacturing

Abstract

3D printing has revolutionized the manufacturing of volumetric components and structures in many areas. Several fully volumetric light‐based techniques have been recently developed thanks to the advent of photocurable resins, promising to reach unprecedented short print time (down to a few tens of seconds) while keeping a good resolution (around 100 μm). However, these new approaches only work with homogeneous and relatively transparent resins so that the light patterns used for photo‐polymerization are not scrambled along their propagation. Herein, a method that takes into account light scattering in the resin prior to computing projection patterns is proposed. Using a tomographic volumetric printer, it is experimentally demonstrated that implementation of this correction is critical when printing objects whose size exceeds the scattering mean free path. To show the broad applicability of the technique, functional objects of high print fidelity are fabricated in hard organic scattering acrylates and soft cell‐laden hydrogels (at 4 million cells mL −1 ). This opens up promising perspectives in printing inside turbid materials with particular interesting applications for bioprinting cell‐laden constructs.

Volumetric Bioprinting of Organoids and Optically Tuned Hydrogels to Build Liver‐Like Metabolic Biofactories

“…Recent research efforts are introducing novel algorithms for tomographic printing that can correct for scattering events at the filtered projection‐level, and thus ensure high resolution printing even in opaque media. [ 36 ] Although this has been only shown with resins carrying homogenously sized particles so far, [ 36 ] future translation to materials laden with cells, which have more complex light‐scattering profiles, will help expand the range of applications of VBP.…”

“…Notably, this approach for optical tuning of the biomaterials could potentially be combined with upcoming software‐end based algorithms to further enhance printing resolution. [ 36 ]…”

Tomographic Volumetric Additive Manufacturing of Silicon Oxycarbide Ceramics

“…Regarding this point, the resin is highly transparent and presents only little absorbance coming from TPO, as shown in Figure S1a–c, Supporting Information. Although relatively low, this attenuation can hinder the printability of centimeter‐scale shapes (Figure S1d, Supporting Information); thus, we correct for it following the method described in the study by Madrid‐Wolff et al [ 22 ] Also, the resin we use has a viscosity of 873 mPa s, as shown in Figure S2a–b, Supporting Information, which is high enough to prevent sinking of the polymerized part within the printing times of 30–60 s (see Figure S2c–e, Supporting Information). The acrylate‐mediated photopolymerization exhibits a thresholded response to light dose [ 25 ] (Figure S1b, Supporting Information).…”

“…Finally, the inverse Fourier transform of these patterns was calculated. Additional corrections for attenuation from the photoinitiator were also performed following the study of Madrid‐Wolff et al [ 22 ]…”

“…[ 18 ] Furthermore, this printing approach allows the fabrication of convoluted hollow structures and geometries with large overhangs which are unprintable with other conventional AM techniques. Recent progress in volumetric additive manufacturing now allows printing different materials including acrylic, [ 19 ] thiol‐ene photoresins, [ 21 ] or even scattering resins, [ 22 ] but to our knowledge the 3D printing of ceramics with a tomographic approach has not been reported yet.…”