Abstract Using near-infrared (NIR) laser to induce polymerization of photosensitive resin containing upconversion microparticles can effectively solve the problem of limited curing depth in traditional stereolithography (SLA). But for an accurate printing structure, in addition to the curing depth, the cross-section diameter is also an important factor. In this study, NaYF4:Yb3+,Tm3+ upconversion microparticles with different Tm3+ concentrations (0.2 mol%, 1.2 mol% and 1.7 mol%) were prepared at different hydrothermal temperatures (150 °C and 200 °C), respectively. The synthesized microparticles were added to the photosensitive resin with different concentrations (0.0625 wt%, 0.125 wt%, 0.25 wt%, 0.5 wt% and 1.0 wt%) and irradiated with a 975 nm semiconductor laser to observe the curing phenomenon. The effects of the fluorescence properties and concentration of upconversion microparticles on the curing depth and cross-section diameter were investigated. Results showed that the curing depth could reach 41 mm and the curing cross-section diameter could be as small as 0.22 mm. And it was easy to control the curing depth and cross-section diameter by changing the Tm3+ concentration, hydrothermal temperature and upconversion microparticles' concentration. Therefore, upconversion microparticles and their concentration can be reasonably selected according to the different requirements of the printed structure. Finally, 3D objects with different heights and finenesses were printed.

中文翻译：

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NaYF4:Yb3+,Tm3+上转换微粒的水热合成及其对立体光刻聚合的影响

摘要 利用近红外（NIR）激光诱导含有上转换微粒的光敏树脂聚合，可以有效解决传统立体光刻（SLA）固化深度有限的问题。但对于精确的印刷结构，除了固化深度外，横截面直径也是一个重要因素。本研究分别在不同的水热温度（150℃和200℃）下制备了不同Tm3+浓度（0.2mol%、1.2mol%和1.7mol%）的NaYF4:Yb3+、Tm3+上转换微粒。将合成的微粒以不同浓度（0.0625wt%、0.125wt%、0.25wt%、0.5wt%和1.0wt%）加入到光敏树脂中，并用975nm半导体激光器照射以观察固化现象。研究了荧光性质和上转换微粒浓度对固化深度和横截面直径的影响。结果表明，固化深度可达41 mm，固化截面直径可小至0.22 mm。并且通过改变Tm3+浓度、水热温度和上转换微粒浓度，易于控制固化深度和横截面直径。因此，可以根据印刷结构的不同要求合理选择上转换微粒及其浓度。最后，打印出具有不同高度和精细度的 3D 对象。结果表明，固化深度可达41 mm，固化截面直径可小至0.22 mm。并且通过改变Tm3+浓度、水热温度和上转换微粒浓度，易于控制固化深度和横截面直径。因此，可以根据印刷结构的不同要求合理选择上转换微粒及其浓度。最后，打印出具有不同高度和精细度的 3D 对象。结果表明，固化深度可达41 mm，固化截面直径可小至0.22 mm。并且通过改变Tm3+浓度、水热温度和上转换微粒浓度，易于控制固化深度和横截面直径。因此，可以根据印刷结构的不同要求合理选择上转换微粒及其浓度。最后，打印出具有不同高度和精细度的 3D 对象。可根据印刷结构的不同要求合理选择上转换微粒及其浓度。最后，打印出具有不同高度和精细度的 3D 对象。可根据印刷结构的不同要求合理选择上转换微粒及其浓度。最后，打印出具有不同高度和精细度的 3D 对象。