A Multiphase Printing Process for Freeform Optics Manufacturing

自由曲面光学可以通过使用更少的光学元件形成具有更小像差的高质量图像。目前，自由曲面光学元件的制造是非常耗时的。液滴按需印刷已被用于制造具有简单曲率的球形或非球面微透镜，但由于对称表面张力的限制，无法生产更复杂的设计。通过施加外部界面力，可以克服这种约束，形成自由形状。该奖项支持一种新型多相印刷工艺的基础研究，该工艺集成了直接印刷和界面力，以制造高精度的自由曲面微光学。该项目将为低成本、高质量的光学产品提供一种新的高精度制造工艺，从而使美国光学工业受益。研究结果可以很容易地应用于其他利用可调界面力的制造领域，例如，航空航天，汽车和生物医学行业中光滑流线表面的3D打印。研究目标是建立(1)透镜表面曲率与多相条件（如支撑液相的厚度和倾斜）之间的关系；(2)自由曲面透镜轮廓与液滴动态变形之间的关系；(3)自由透镜形状与非均匀材料性能（如液滴表面同时存在不同的表面张力和粘度）之间的关系。实验将在混合多相印刷平台上进行。在该平台上，将在不同的多相条件下，在固-液-气或液-气多相表面上打印紫外线固化单体液滴。采用精密的线性倾斜工作台来控制支撑液相的厚度和倾斜。透镜表面曲率将由白光干涉仪和Twyman-Green和Mach-Zehnder干涉仪组合测量。为了实现第一个目标，单体液滴在多相表面达到平衡状态后进行固化。将采用有限元法确定不同多相条件下的透镜轮廓曲率。为了实现第二个目标，单体液滴将在瞬态固化。将安装高速摄像机来识别液滴的瞬态形状。在不同瞬态下获得的镜头轮廓将被分析并与高速图像相关联。为了实现第三个目标，将使用无掩模光刻技术来调整单体液滴的局部表面张力和粘度，以实现不均匀的性能，这将导致不均匀的液滴变形。

Freeform optics can form high quality images with smaller aberrations by using fewer optical components. At the present time, fabrication of a freeform optical component is extremely time consuming. Drop-on-demand printing has been used to fabricate spherical or aspherical microlenses with simple curvatures, but is not able to produce more complicated designs due to the constraint of symmetric surface tension forces. By applying external interfacial forces, this constraint can be overcome and freeform shapes can be formed. This award supports fundamental research of a novel multiphase printing process that integrates direct printing and interfacial forces in order to fabricate high precision freeform micro optics. This project will benefit the U.S optical industry by providing a new high precision manufacturing process for low-cost and high quality optical products. Research results can be readily applied to other manufacturing areas that utilize tunable interface forces, for example, 3D printing of smooth streamline surfaces in aerospace, automobile, and biomedical industries.The research objectives are to establish relationships (1) between lens surface curvatures and the multiphase conditions (such as thickness and tilting of the supporting liquid phase); (2) between freeform lens profiles and dynamic deformation of droplets; and (3) between the freeform lens shapes and non-uniform material properties (e.g. different surface tension and viscosity coexisted on the droplet surface). Experiments will be conducted on a hybrid multiphase printing platform. On this platform, ultraviolet curable monomer droplets will be printed on a solid-liquid-air or liquid-air multiphase surface under different multiphase conditions. A precision linear and tilting stage will be used to control the thickness and tilting of the supporting liquid phase. Lens surface curvatures will be measured by a white light interferometer and a combined Twyman-Green and Mach-Zehnder interferometer. To achieve the first objective, monomer droplets will be cured after the droplets reaching equilibrium status on the multiphase surface. Finite element method will be used to determine lens profile curvatures under different multiphase conditions. To achieve the second objective, monomer droplets will be cured at transient state. A high speed camera will be installed to identify the droplet transient shape. Lens profiles obtained at different transient state will be analyzed and correlated to high speed images. To achieve the third objective, maskless lithography will be used to tune the local surface tension and viscosity of the monomer droplet to achieve non-uniform properties, which will cause non-uniform droplet deformation.