Study on High Resolution Photoforming for Micromachines

在微机械制造中应用光成形技术需要10mum以下的成形分辨率。为了获得最佳尺寸和形状的固化细胞，我们考虑了光固化树脂的固化机理，并建立了一个用改进的蒙特卡罗方法跟踪光子行为的计算机模型。我们模拟了大量光子的行为，得到了吸收光子的密度分布和使固化层深度保持在10mum以下的条件。从这些理论研究中，我们得出了以下条件：(1)稳定曝光光斑直径，(2)精细控制曝光光量，(3)树脂更多的光吸收系数。在此基础上，我们设计了两种光成形装置，a) He-Cd激光和紫外光固化树脂，b) Ar^+激光和可见光固化树脂与有机染料。我们用该仪器检查了成型实验，得到了以下分辨率：He-Cd激光与紫外光固化树脂在水平方向上约10mum，在垂直方向上约30mum； Ar^+激光与可见光固化树脂与有机染料在水平方向上约2mum，在垂直方向上约5mum。在可见光情况下，没有发现紫外线情况下形成的冰柱等不必要的部分。在最大应变低于2%的情况下，成功地制作了显微活动机构，并在10,000次操作中没有出现故障。

A forming resolution under 10mum is required for application of photoforming to micromachine manufacturing. For the purpose of obtaining the optimum dimensions and shape of solidified cells, we considered a solidification mechanism of light-cured resin and developed a computer model tracing the behaviors of photons with a modified Monte Carlo method. We simulated the behaviors of a large number of photons and obtained the density distribution of absorbed photons and conditions to keep the depth of a solidified layr under 10mum. From these theoretical studies, we arrived at the following conditions ; (1) stabilization of exposure spot diameter, (2) fine control of exposure light amount, (3) more light absorption factor of the resin.Based on these guidelines, we designed the photoforming apparatus which enabled to experiment two kinds of combinations, a) He-Cd laser and ultraviolet light curing resin, and b) Ar^+laser and visible light curing resin with organic dyes. We examined forming experiments using the apparatus and obtained the following resolutions ; about 10mum in the horizontal direction, and about 30mum in the vertical direction by the combination of He-Cd laser and ultraviolet light curing resin, and about 2mum in the horizontal direction and about 5mum in the vertical direction by the combination of Ar^+laser and visible light curing resin with organic dyes. In the visible light case, unnecessary parts like icicles formed in the ultra violet light case were no more found. Microscopic movable mechanisms were successfully fabricated and endured in 10,000 operations without failure when maximum strain was kept under 2% strain.