title: High-performance 3D printing of hydrogels by water-dispersible photoinitiator nanoparticles.
abstract: In the absence of water-soluble photoinitiators with high absorbance in the ultraviolet (UV)-visible range, rapid three-dimensional (3D) printing of hydrogels for tissue engineering is challenging. A new approach enabling rapid 3D printing of hydrogels in aqueous solutions is presented on the basis of UV-curable inks containing nanoparticles of highly efficient but water-insoluble photoinitiators. The extinction coefficient of the new water-dispersible nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is more than 300 times larger than the best and most used commercially available water-soluble photoinitiator. The TPO nanoparticles absorb significantly in the range from 385 to 420 nm, making them suitable for use in commercially available, low-cost, light-emitting diode-based 3D printers using digital light processing. The polymerization rate at this range is very fast and enables 3D printing that otherwise is impossible to perform without adding solvents. The TPO nanoparticles were prepared by rapid conversion of volatile microemulsions into water-dispersible powder, a process that can be used for a variety of photoinitiators. Such water-dispersible photoinitiator nanoparticles open many opportunities to enable rapid 3D printing of structures prepared in aqueous solutions while bringing environmental advantages by using low-energy curing systems and avoiding the need for solvents.
authors.affiliation: Casali Center of Applied Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Amol A
authors.initials: AA
authors.lastname: Pawar
authors.affiliation: Casali Center of Applied Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Saada
authors.affiliation: Casali Center of Applied Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Ido
authors.initials: I
authors.lastname: Cooperstein
authors.affiliation: Casali Center of Applied Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Liraz
authors.initials: L
authors.lastname: Larush
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.; School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Jackman
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.; School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore.
authors.forename: Seyed R
authors.identifier: 0000-0002-2857-786X
authors.initials: SR
authors.lastname: Tabaei
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.; School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore.
authors.forename: Nam-Joon
authors.initials: NJ
authors.lastname: Cho
authors.affiliation: Casali Center of Applied Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Shlomo
authors.initials: S
authors.lastname: Magdassi
mesh_terms: D020100:Hydrogels / Q000737:chemistry* / Q000528:radiation effects; D053758:Nanoparticles / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry; D058567:Photoinitiators, Dental / Q000737:chemistry / Q000528:radiation effects; D066330:Printing, Three-Dimensional; D023822:Tissue Engineering; D014466:Ultraviolet Rays; D014867:Water
chemical_list: C520678:(2,4,6-trimethylbenzoyl) diphenylphosphine oxide; D020100:Hydrogels; D010720:Phosphines; D058567:Photoinitiators, Dental; D014867:Water
keywords: 3D printing; TPO; UV curing; hydrogels; photoinitiator