Cheng He, Xia Chun, Zhang Meng, Kuebler Stephen M, Yu Xiaoming
Appl Opt. 2019 May 1;58(13):D91-D97. doi: 10.1364/AO.58.000D91.
Microfabrication based on photopolymerization is typically achieved by scanning a focal spot within the material point by point, which significantly limits fabrication speed. In this paper, we explore a method for rapid fabrication of high-aspect-ratio microstructures based on photopolymerization using a femtosecond laser beam that is converted into a Bessel beam by an axicon. With stationary exposure, a polymer fiber measured at 200 μm in length and 400 nm in width (500∶1 aspect ratio) was fabricated within 50 ms of exposure time. The exposure conditions can be adjusted to produce fibers with variable widths. A phenomenological polymerization-threshold model is adapted for Bessel-beam exposure. The revised model is applied to analyze the structure width and estimate the order of multi-photon absorption. Examination of the cross section of the fibers shows that they are nearly monolithic, suggesting that active species diffuse during photopolymerization. By scanning the Bessel beam in the plane transverse to the direction of beam propagation, mesh structures are fabricated with a single-pass scan, showing the potential of this method for rapid fabrication of large-scale high-aspect-ratio microstructures for applications in photonics, micro-machines, and tissue engineering.
基于光聚合的微纳制造通常是通过在材料内逐点扫描焦点来实现的，这极大地限制了制造速度。在本文中，我们探索了一种基于光聚合的高纵横比微结构快速制造方法，该方法使用飞秒激光束，通过轴棱锥将其转换为贝塞尔光束。通过固定曝光，在50毫秒的曝光时间内制造出了长度为200微米、宽度为400纳米（纵横比为500∶1）的聚合物纤维。可以调整曝光条件以生产宽度可变的纤维。采用现象学聚合阈值模型对贝塞尔光束曝光进行分析。将修正后的模型应用于分析结构宽度并估计多光子吸收的阶数。对纤维横截面的检查表明，它们几乎是整体式的，这表明活性物种在光聚合过程中会扩散。通过在垂直于光束传播方向的平面内扫描贝塞尔光束，单次扫描即可制造出网格结构，这表明该方法在光子学、微机械和组织工程等应用中快速制造大规模高纵横比微结构方面具有潜力。
