Photopolymerization 3D printing of luminescent ceramics

ZnS/CaZnOS:Mn2+ luminescent ceramic components exhibit both photoluminescence (PL) and mechanoluminescence (ML). A PL material luminesces upon optical irradiation, whereas ML material converts mechanical energy into optical energy. ML materials have important application prospects in new light sources, damage detection, healthcare and anti-counterfeit encryption. In this paper, we report the preparation of luminescent ZnS/CaZnOS:Mn2+ ceramic parts via vat photopolymerization 3D printing and discuss possible applications. We use manganese-doped zinc sulphide/zinc calcium oxysulfide powder as the raw luminescent ceramic powder and investigate the slurry preparation, vat photopolymerization 3D printing and sintering to fabricate photoluminescent and ML ceramic prototypes. The powder particle size was 9–10 µm, the coupling agent was 4 wt% silane (KH-570), and the photoinitiator was 2 wt% diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide. The result is a manganese-doped photosensitive slurry with uniform stability and fluidity, a solid content of 50 vol%, and a viscosity of 3 Pa·s. This slurry has excellent characteristics for vat photopolymerization 3D printing, with a penetration depth Cd = 35.03 µm and a theoretical exposure energy Ec = 2.26 mJ/cm2. ZnS/CaZnOS:Mn2+ parts manufactured in this study exhibit both PL when irradiated by a light source and ML when extruded and rubbed. The photon intensity as high as 200 × 105 is released from ZnS/CaZnOS:Mn2+ when irradiated at 339 nm, which is nearly 50% more than that released when irradiated at 290 nm. The intensity of ML photons emitted increases with the applied mechanical force, with up to 1700 intensity emitted. Conventional forming methods mainly involve coating parts with luminescent materials mixed with polydimethylsiloxane polymer, surrounding ZrO2 cores by a shell layer of ML hybrid material and other traditional processes, which cannot produce complex structures or provide long-lasting luminescence. This study thus combines the luminescent material ZnS/CaZnOS:Mn2+ and vat photopolymerization 3D printing to produce complex parts with low surface roughness (Sa = 5.92 µm and Sz = 53.11 µm before sintering, and Sa = 5.09 µm and Sz = 50.73 µm after sintering) and high chemical stability. These results expand the applications of ZnS/CaZnOS-based luminescent ceramic materials and vat photopolymerization 3D printing.