由層厚控制探討光柵結構之繞射與應變響應特性

Abstract

本研究基於LCD光固化積層製造技術，探討光固化列印成品因成化程度不同導致折射率的不同，產生類似於繞射光柵之效應，並評估其在應變感測應用中的可行性。列印系統使用UniFormation GKtwo 8K光固化3D列印機，其矩陣式紫外光源透過LCD面板遮罩投影圖案至光敏樹脂中，進行逐層固化，成型完成後之樣品進行研磨與拋光處理，藉以去除表面層紋與雜散光影響，顯著提升透光性與繞射品質。 實驗中採用紅光與綠光雷射照射表面處理後樣品，並觀察繞射條紋圖樣與間距變化，發現不同切層厚度（3、5、10、25、50 、100µm）對繞射條紋的清晰度與主峰距離具顯著影響。將條紋影像轉換為灰階圖去分析條紋間距，並與理論繞射間距進行比對。同時設計標準拉伸試片（依ISO 527-2規範），施加軸向張力並即時紀錄繞射圖樣之變化。 結果顯示，在拉伸過程中，繞射條紋主峰間距隨應變增加而接近線性展寬，VER試片表現出較佳的敏感性與解析度，說明列印方向與內部結構排列對繞射感測結果具有重要影響。實驗亦探討不同預載條件下的感測穩定性，驗證其在重複性與線性響應上具備應用價值。

This study is based on the LCD photocuring lamination manufacturing technology. It explores the effect of different refractive indices of photocuring printed products due to different curing degrees, which produces a diffraction grating effect, and evaluates its feasibility in strain sensing applications.The system employed is a UniFormation GKtwo 8K LCD resin printer, featuring a matrix UV light engine projecting sliced images through an LCD mask to selectively cure photopolymer resin layer by layer. Post-processing via mechanical polishing and diamond slurry lapping effectively removed surface striations, significantly improving transparency and diffraction performance. Laser diffraction experiments were conducted using red and green lasers to illuminate the printed samples. Variations in printing layer thickness (3, 5, 10, 25, 50, 100 µm) led to distinct changes in fringe clarity and peak spacing. Fringe patterns were captured and analyzed using grayscale image processing techniques, with experimental spacing trends aligning closely with theoretical diffraction predictions. Standard tensile test specimens (ISO 527-2 Type V) were subjected to axial loading. Dynamic fringe spacing shifts were recorded throughout the tensile deformation. The results revealed a clear linear relationship between applied strain and diffraction fringe spacing, particularly in VER-oriented samples, which exhibited higher sensitivity and resolution. The sensing mechanism was found to be strongly influenced by the printing direction and internal microstructure. Pre-load sensitivity tests further confirmed the repeatability and stability of the optical response, suggesting feasibility for non-contact strain measurement.