Rapid Three-Dimensional Printing in Water Using Semiconductor–Metal Hybrid Nanoparticles as Photoinitiators

Abstract

Additive manufacturing processes enable fabrication of complex and functional three-dimensional (3D) objects ranging from engine parts to artificial organs. Photopolymerization, which is the most versatile technology enabling such processes through 3D printing, utilizes photoinitiators that break into radicals upon light absorption. We report on a new family of photoinitiators for 3D printing based on hybrid semiconductor-metal nanoparticles. Unlike conventional photoinitiators that are consumed upon irradiation, these particles form radicals through a photocatalytic process. Light absorption by the semiconductor nanorod is followed by charge separation and electron transfer to the metal tip, enabling redox reactions to form radicals in aerobic conditions. In particular, we demonstrate their use in 3D printing in water, where they simultaneously form hydroxyl radicals for the polymerization and consume dissolved oxygen that is a known inhibitor. We also demonstrate their potential for two-photon polymerization due to their giant two-photon absorption cross section.

A Versatile 3D and 4D Printing System through Photocontrolled RAFT Polymerization

“…Spatially controlled light intensities have been previously explored by several groups for controlling the mechanical properties of 3D materials prepared by conventional photopolymerization, and even for 4D printing via swelling and dehydration induced actuation. [3e,25] As the mechanical properties of our 3D printed materials were dependent on the light exposure,w ed ecided to exploit these differences to print am aterial with spatially resolved properties.F urthermore, our resin formulations were water soluble,w hich allowed objects to be printed in aqueous solutions.T od ate,o nly ah andful of aqueous 3D printing systems have been developed [26] due to the insolubility of typical photoinitiators and monomers in water, however, the current system tailors toward 3D bioprinting due to the high biocompatibility of aqueous systems. [3h,m,n, 27] To demonstrate the utility of our formulation, ahydrogel with spatially resolved properties was 3D printed and subsequently dehydrated and re-swelled for actuation;assuch, a4Dprinted material was fabricated using our photosensitive resin.…”

Light‐Induced Tuning and Reconfiguration of Nanophotonic Structures

“…Unlike conventional photo‐initiators that are consumed upon irradiation, these particles form radicals through a photocatalytic process and possess giant two‐photon absorption cross section. Namely, enhanced light absorption by the semiconductor nanorod is followed by charge separation and electron transfer to the attached metallic nanoparticle, enabling redox reactions to form radicals …”

“…Namely, enhanced light absorption by the semiconductor nanorod is followed by charge separation and electron transfer to the attached metallic nanoparticle, enabling redox reactions to form radicals. [166]…”

Patterning of Nanoparticle‐Based Aerogels and Xerogels by Inkjet Printing

“…Plenty of scientists are using inkjet printing for the deposition of metal NCs or semiconductor NCs to manufacture structured electronic components for chip design and sensing . In addition, some works on laser induced 3D printing for the fabrication of porous materials can be found . Semiconductor NCs are of high interest, since the interconnection of crystal size, and shape and the optoelectronic properties defined by the quantum confinement effects diversifies the field of obtainable systems .…”