利用上转换纳米颗粒的多光子聚合用于可调特征尺寸打印
Multi-photon polymerization using upconversion nanoparticles for tunable feature-size printing
AI总结：
本研究针对双光子打印依赖昂贵飞秒激光器的局限，探究基于上转换纳米颗粒的多光子聚合机制，证实可通过调节近红外功率在不改变聚合度的情况下调控体素尺寸，为低成本高速精细3D打印提供新路径。
摘要：
基于光的3D打印技术的最新发展标志着增材制造的一个转折点。通过光聚合作用，液态树脂可被固化为复杂物体。通常，聚合反应通过用紫外（UV）光或蓝光激发光引发剂来触发。在双光子打印（TPP）中，激发通过双光子的非线性吸收实现；它能够打印100纳米的体素，但需要昂贵的飞秒激光器，这严重限制了其广泛普及。上转换纳米颗粒（UCNPs）最近被提出作为TPP的光聚合替代方案，但使用的是连续波激光器。UCNPs将近红外（NIR）光转换为可见光/紫外光，从而像TPP一样在局部引发聚合反应。本文对这种多光子机制开展了研究，并论证了非线性特性如何影响打印过程。具体而言，我们报道了通过调节近红外激发强度来精细调整打印体素尺寸的可能性。使用明胶基水凝胶，我们能够在不改变聚合度的情况下，通过调节近红外功率将横向体素尺寸从1.3μm调整到2.8μm，轴向尺寸从7.7μm调整到59μm。这项工作为使用廉价光源在保持最小特征尺寸的同时加快制造速度开辟了新的机遇。
英文摘要：
The recent development of light-based 3D printing technologies has marked a turning point in additive manufacturing. Through photopolymerization, liquid resins can be solidified into complex objects. Usually, the polymerization is triggered by exciting a photoinitiator with ultraviolet (UV) or blue light. In two-photon printing (TPP), the excitation is done through the non-linear absorption of two photons; it enables printing 100-nm voxels but requires expensive femtosecond lasers which strongly limits their broad dissemination. Upconversion nanoparticles (UCNPs) have recently been proposed as an alternative to TPP for photopolymerization but using continuous-wave lasers. UCNPs convert near-infrared (NIR) into visible/UV light to initiate the polymerization locally as in TPP. Here we provide a study of this multi-photon mechanism and demonstrate how the non-linearity impacts the printing process. In particular, we report on the possibility of fine-tuning the size of the printed voxel by adjusting the NIR excitation intensity. Using gelatin-based hydrogel, we are able to vary the transverse voxel size from 1.3 to 2.8 μm and the axial size from 7.7 to 59 μm by adjusting the NIR power without changing the degree of polymerization. This work opens up new opportunities for speeding up the fabrication while preserving the minimum feature size with cheap light sources.
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