On-Demand Activation of Photochromic Nanoheaters for High Color Purity 3D Printing

Abstract

The creation of white and multicoloured 3D-printed objects with high colour fidelity via powder sintering processes is currently limited by discolouration from thermal sensitizers used in the printing process. Here we circumvent this problem by using switchable, photochromic tungsten oxide nanoparticles, which are colourless even at high concentrations. Upon ultraviolet illumination, the tungsten oxide nanoparticles can be reversibly activated making them highly absorbing in the infrared. Their strong infrared absorption upon activation renders them efficient photothermal sensitizers that can act as fusing agents for polymer powders in sintering-based 3D printing. The WO3 nanoparticles show fast activation times, and when mixed with polyamide powders they exhibit a heating-to-colour-change ratio greatly exceeding other sensitizers in the literature. Upon mixing with coloured inks, powders containing WO3 display identical colouration to a pristine powder. This demonstrates the potential of WO3, and photochromic nanoparticles in general as a new class of material for advanced manufacturing.

Nanoscale thermoplasmonic welding

“…This phenomenon makes thermoplasmonic welding a potential technology to weld materials at low light power with minimal damage ( Figure 9 A). As shown in Figure 9 B, the color of printed matter depends to some extent on the writing speed of the laser, because this defines the welding degree ( Powell et al., 2020 ). The nanocomposites mixed with the plasmonic materials with polyamide powder could be made into vivid objects, showing colorful effects ( Figures 9 C and 9D) ( Powell et al., 2018 ).…”

“… (C) Welded samples produced with different materials. Reprinted and adapted with permission from Powell et al. (2020 ) Copyright 2020, American Chemical Society.…”

UV Photochromism in Transition Metal Oxides and Hybrid Materials

“…[ 14 ] As the field evolved, more work was conducted on improving photochromic response and performance. These involve structural and morphological control of preparation, [ 15,16 ] employing advanced micro/nanofabrication techniques, [ 17,18 ] compositing oxides with organic materials, [ 19 ] compositing of several oxides, [ 20 ] elemental doping, [ 21 ] and embedding chromic oxide materials into polymer matrices. [ 22,23 ] These techniques have enhanced the performance of photochromic oxides in terms of sensitivity, [ 24 ] responsivity, [ 25 ] flexibility, [ 26 ] and dynamic range.…”

Tunable Photothermal Actuation Enabled by Photoswitching of Donor–Acceptor Stenhouse Adducts

“…We have recently demonstrated how the controllable photothermal properties, negative photochromism, and high molar absorptivity of DASAs could be leveraged to achieve self-regulating control of fluid motion . In conceptually related work, the use of switchable tungsten­(VI) oxide nanoparticles, WO 3 , has been recently used as a photothermal sensitizer for high color quality 3D printing …”

“…36 In conceptually related work, the use of switchable tungsten(VI) oxide nanoparticles, WO 3 , has been recently used as a photothermal sensitizer for high color quality 3D printing. 37 Herein, we report the development and use of a DASA− polymer conjugate in the solid state to enable tunable, loadbearing actuation to produce mechanical work. We demonstrate visible light-powered actuation performance with a cantilever capable of lifting a weight against gravity and a remotely powered and controlled crawler.…”