Water-dispersible photo-initiator nanoparticles for 2D and 3D printing

Magdassi Shlomo, HUJI, Faculty of Science, The Institute of Chemistry

Highly-reactive photoinitiator nanoparticles were developed, enabling fast 2D and 3D printing of water-based inks, including hydrogels



Hydrogels, scaffolds for tissue engineering, soft tissue engineering, tissue regeneration, 3D printing in water, 4D printing, additive manufacturing, digital 3D design, stereo-lithography, stimuli-sensitive materials, biomedical devices, bio-compatible materials, biodegradable materials, cell-compatible hydrogels, bio-responsive hydrogels, biological hydrogels, UV inks.

Development Stage

Proof of concept and initial results

Patent Status

PCT application filed

Innovation summary

We have developed innovative photoinitiator nanoparticles, which can be added to water-based UV-curable inks to enable rapid 3D printing. These inks can be used for printing 3D hydrogels intended for various tailor-made photosensitive applications, such as tissue engineering, and any application requiring water-based UV-curable ink.  


Our innovation enables rapid printing at remarkably low-costs, using aqueous inks and a DLP (digital light-processing) 3D printer. These new water-insoluble photo-initiators (PIs) contained in the ink, have high absorbance in the UV-visible range – 300 times higher than the best commercially available water-soluble PIs. This results in a remarkably fast polymerization rate, eliminating the need to add solvents – which, until now could not be avoided in 3D printing – thereby, providing a low-energy curing method. This innovation circumvents the known lack of highly-efficient water-insoluble PIs with high absorbance in the UV-visible range.


Movie demo: https://www.youtube.com/watch?v=nJmrm4DShdo



The printing utilizes a photo-polymerization process, using a light-emitting diode-based DLP printer. An aqueous ink solution is prepared by mixing and stirring a reactive monomer or oligomer, together with highly reactive PI nanoparticles containing trimethylbenzoyl-diphenylphosphine oxide (TPO) and water – at room temperature.


The TPO nanoparticles are prepared by rapid conversion of volatile micro-emulsions into a water-dispersible powder – a process which can be used for a variety of PI types. These TPO nanoparticles absorb a considerable amount of UV light in the range between 385-420 nm. The polymerization rate at this range is very fast, eliminating the need to add solvents. The technology for making the nanoparticles is suitable to a variety of water insoluble photoinitiators, including mixtures.




  • Fast, low-cost 3D printing of hydrogels, utilizing highly accessible DLPs, as compared to costly, complex 3D and 4D printing processes
  • High-resolution printing of hydrogels in predefined dimensions and porosity levels
  • Aqueous hydrogels that swell but do not dissolve in water
  • Flexible design of diversified, tailor-made applications
  • Low-energy curing method reduces fabrication time and costs
  • Energy-efficient process generates near-zero waste
  • Non-toxic, bio-compatible materials - suitable for medical applications
  • Eco-friendly materials which do not contain solvents
  • UV-curable inks can be used for 2D printing


Development milestones

A proof of concept was achieved by preparing and using water-dispersible photoinitiator nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) which is considered the most efficient photoinitiator in initiating free radical polymerization. These TPO nanoparticles enabled rapid 3D printing of complex hydrogel structures in water using SLA-based low-cost 3D printers, without any organic solvent. To the best of our knowledge and experience, this process is impossible to perform with presently available PIs and water-soluble monomers.



  • Hydrogel scaffolds for tissue engineering
  • Hydrogels for other bio-medical applications
  • 3D and 2D printing using water-based UV inks for diverse applications


Researcher information   https://scholars.huji.ac.il/magdassi

Patent Status

Published 3380893

Contact for more information:

Matt Zarek
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